Sonic the Hedgehog 3C Prototype 0517 for the Sega Mega Drive/Genesis was released by drx during the February 23rd, 2008 proto release. An earlier in-development beta with a compilation number of 0408 was also found. When this beta was obtained by drx the file was labeled 3C indicating this was an unreleased version of Sonic 3. Due to the late development date (dating after Sonic 3's release), it's obvious this isn't Sonic 3 before it was split into 2 games.
Level Select: Enabled by default. Just scroll down on the start menu.
Debug Mode: Debug is enabled by default. Just hold while selecting a level on the Level Select screen. The ring counter will be replaced with a player sprite/frame counter.
All Chaos Emeralds: At the sound test screen, play songs 02, 04, 06, 08.
Knuckles is a selectable character in the one player mode.
All the explosions are black when debug mode is enabled.
In the sound test anything from D9 through FE has no sound. The final sound F is the "Sega" sound.
The music locations are ALMOST the same in Sonic 3K and this beta; The only differences are that all of the songs (except the first occurrence of the Act 1 Boss theme) use the Sonic 3 versions, and that the original Sonic 3 credits located at $26 is replaced with the new Credits medley.
The victory music usually played after beating the Launch Base boss before going to the credits in Sonic 3 is more developed, but can only be heard by listening to the credits music.
The echo track of Flying Battery Zone's Act 1 music will go off sync after two loops, and slowly gain drag behind the lead melody.
Final credits medley in this prototype
The final credits medley is longer, different, and uses a few additional segments from additional zones.
If the game is beat all the way through on a save file, only Sonic 3 levels can be selected.
The save data screen does not show the number of lives and continues. Sonic 3 did not show this, either. Sonic 3 & Knuckles does show this. Also, there are only 6 save slots, while in Sonic 3&K there are 8. (Sonic 3 Final actually had 14 save images; 6 for S3 only, 8 for Sonic 3&K.
The Emeralds seem to activate an incomplete version of Hyper mode. For Sonic, it uses the rainbow palette and gives him the dash attack, but doesn't give him the star effect or the flash and sparks when the dash attack is performed. For Tails, it neglects to give him his Flickies or the trailing sparks. For Knuckles, it adds the shockwave to latching onto walls, but doesn't replace the trailing sparks with afterimages. And for all of the incomplete Hyper forms, none can automatically breathe underwater.
The S monitor makes the characters take their Hyper form, rather than Super as in Sonic 3 final.
Hyper Sonic's stars around his body are completely different than in the final.
Unlike in final versions, if the "S" monitor is used with Knuckles, Hyper Knuckles WILL cause an earthquake when gliding for a distance into a wall.
Interesting thing about this build is that there is a Tails transformation with only Chaos Emeralds. It's basically Super Tails without the birds. However using an S monitor and Super Tails will have the birds (perhaps there was a super and hyper version of Tails planned at one point).
If the game is beaten with the seven Chaos Emeralds, at the end of the staff credits, instead of the Sonic the Hedgehog 3 logo appearing, the "TRY AGAIN" screen with Robotnik and Knuckles will still appear, but Knuckles will juggle no Chaos Emeralds.
On the Glowing Spheres stage, aside from having a different layout and the items falling downward, there's a chance you'll get a green ball with an F on it. It only makes the bumper sound the black ones make.
Entering the Glowing Spheres level makes you lose all your rings.
The slots stage has a completely different layout and the background freezes when you spin the reels.
Entering the gumball bonus stage makes you lose your shield. Not sure about the other ones.
While all three bonus stages are implemented, you can access one randomly once you hit 50 rings.
The first time entering Special Stage 2 on the Sound Test leads to a unused Super Emerald Stage. Essentially it's just a giant maze, which has no rings, although for some reason you don't get a Perfect. It gives you a Super Emerald like normal. A different Special stage is chosen each time you enter it.
In Angel Island zone (and maybe every other zone), when the miniboss is finished and the signpost twirls down to the ground, if a power-up monitor shows up, sometimes it lands behind the sign post. In the final, if the monitor land around the same spot as the sign post, it's in front.
When at the end of the first Hydrocity act, you can die by drowning while it's tallying your score.
When playing as Sonic in Hydrocity Act 1 the boss plays the Sonic 3 Act 1 mini-boss theme instead of the Act 2 boss theme. (Sonic 3 final plays the Act 2 boss theme, but switches to the Sonic & Knuckles miniboss music if the drowning timer starts and you get out of the water, Sonic 3 & Knuckles final plays the Sonic & Knuckles Act 1 mini-boss theme).
When playing as Sonic in Hydrocity Act 2, the spring at the beginning has been replaced with a 1UP, which is the same as Sonic 3 & Knuckles final but not like Sonic 3 final.
The Knuckles MGZ2 boss still plays the miniboss music and doesn't play the "wall breaking" sound when the spikes penetrate the floor or ceiling.
When playing as Sonic in Carnival Night Act 1 Tails randomly appeared after the boss, even though it was Sonic only. (This glitch randomly happens in the completed Sonic 3 but with a different frequency in which it happens)
In Act 1, when Tails first comes down when playing as Sonic and Tails, the graphics are screwed up. The snowboard intro overwrites Tails' tiles with the snowboard's, and when the snowboard disappears, Tails' tiles should load. However, Tails' AI doesn't allow this to happen fast enough, and thus proceeds to draw Tails with some of the snowboard's tiles still remaining. Only when Tails lands does the tile swap complete and Tails return to normal.
When fighting the Act 1 minibosses as Super/Hyper Knuckles, defeating one of the bosses will cause you to revert to normal and play the regular LBZ1 music, as if the boss were defeated. However, you still have to defeat the other boss to continue.
In Act 2, the part between the boss on the level and the ones on the ship is not timed. The timer freezes upon entering the cutscene by stepping into the Eggmobile; it starts up again when you land on the ship. This behavior is exhibited by Sonic 3 & Knuckles, but not by Sonic 3 alone (the timer counts during the cutscene).
In Launch Base 2, as Knuckles, you don't fight the second boss like in S3&K final.
In Mushroom Hill zone act 1: You fall in from the sky just like in the previous beta.
One of the giant rings in Mushroom Hill Zone isn't put in yet, instead it is filled with a diamond pattern of rings.
The super ring before the transition to the boss (before the pully, guarded by that chicken enemy in MHZ2) is gone.
The exit from the highest super ring in MHZ2 is different.
The MHZ2 boss does not have fire effects when killed, and you must hit him 6 times AFTER he has zoomed off.
When playing as Sonic in Mushroom Hill Act 1 The Super Ring at the beginning of the level doesn't seem to flash if you enter here via Level Select with no emeralds. If you go to MH1 with emeralds, the Super Ring flashes, but entering it merely gives you 50 rings. Strangely, the rest of the Super Rings aren't flashing.
Defeating the Flying Battery Act 2 miniboss and dying causes the clouds to mess up.
When playing as Sonic in Flying Battery 2 After defeating the WFZ-style miniboss, the floor begins to move up. In addition, there's a horizontal wall that moves right. Dying here not only garbles the clouds (as mentioned by someone else), it garbles the horizontal wall. Also, Sonic doesn't roll out of the Flying Battery in the level transition - he simply runs out. He appears to be rolling in the Sandopolis intro, though.
You can move the moment you enter Sandopolis act 1 and no longer are forced to wait until you land in the sand and have to pop out.
When playing as Sonic in Sandopolis 1 Sonic doesn't get stuck in the sand after he falls into the level. Also, as MK said, you can move left and right during the intro.
Tails seems to have quite a few collision problems.
When you break the capsule at the end of the boss fight in Act 2, the platform on the screen floats towards the other platforms. You have to jump from platform to platform to get to Hidden Palace unlike in the final. This part is almost unchanged from the 0408 prototype except the transition to Hidden Palace does work.
The Act 3 boss area plays the Act 2 music until you reach Robotnik.
When you beat Robotnik, the lava is still there.
The giant hand miniboss has a few messed up textures.
The Act 3 boss area has a fire shield instead of a lightning shield. The ring pattern is also different.
The platforms in which it is necessary to Spin Dash to go down are much faster.
Act 2's palette is different from the final's, and stays similar to the Act 1 palette in that the rocks are red/brown. Because of this, after beating Act 1's miniboss, the lava doesn't change color, but you can still walk on it as if it was harmless.
When Hidden Palace is entered through a Special Stage Ring, Death Egg music will play. When trying to leave through using the teleporter the game will loop and you will return to Hidden palace.
Hidden Palace (Mushroom Hill) has Death Egg music.
In Hidden Palace Zone, even though the controls are locked during the cutscene, Tails' controls aren't locked, and he will continue to use his AI if the second controller isn't used.
When playing as Sonic in Hidden Palace not only can Knuckles hurt you as Super/Hyper Sonic, Knuckles can hurt you if you're in Debug mode placing an object, at which point Sonic's graphics might be corrupted. (The corruption only seems to happen if you were Super/Hyper Sonic at the time).
Knuckles can punch out Hyper Sonic and Super Tails during the fight in Hidden Palace.
In this version Hidden Palace works exactly like the final, with a couple differences. The HUD is still present (It's green while playing as Knuckles). Death Egg Music is playing (This is due to it coming right after the Death Egg Final Boss level slot in the game). The intro plays every time you enter the chamber. The gray emerald locations don't save after you leave (They reappear after the intro). The laser zaps all the emerald alters even if you already have that emerald (Although it still shows that you have that emerald). There is no Super Emerald screen after you beat a special stage. Also, there are color differences in the beta, probably changed so they could correspond with the colors of the Chaos Emeralds.
Entering from LRZ2 as Knuckles causes Hidden Palace to read as Sky Sanctuary Zone Act 1, Other than this it is the same as the Final.
Sky Sanctuary Zone act 2: The teleporter that usually teleports Knuckles is not present and there seems to be a few missing rings.
When entering Sky Sanctuary 2 with Sonic and Tails, Mecha Sonic has a glitch where there's an invisible wall in between the fighting area. When Mecha Sonic is defeated with Sonic and Tails, the game acts like Sky Sanctuary 1 was completed and doesn't continue to the next level.
Also, when entering Sky Sanctuary Act 2 with Sonic and Tails, Tails is able to jump behind the Floating Island sprite.
The Knuckles-only Metal Sonic boss in Sky Sanctuary freaks out when Tails is used. Once defeated, there is no ending at all.
Pressing down in SSZ close to Knuckles doesn't make him wave yet.
In Doomsday Zone act 2 there is no Doomsday music and Death Egg act 2's music continues playing.
Lots of rings are given at the start of Doomsday Zone because there are none around when chasing Robotnik.
That palette for Doomsday is the same as DEZ2
Also in the Doomsday Zone, when you hit chase Eggman and you hit him, you don't get knocked back like in the final.
When the Doomsday boss is destroyed with tails, the game goes to Level select.
In Doomsday Zone, during the first boss, if you move all the way to left, two missiles can actually be triggered from the end of the asteroid field segment.
The midboss of Death Egg Zone still hits you and you will be knocked out of the Super Sonic form.
Death Egg's Doomsday act 2 boss doesn't play boss music, it just plays DEZ music.
When Robotnik flies away, everything is much slower than the final, and no buttons are pressed it is possible to get stuck in the bottom left unless Debug mode is activated.
If Death Egg's 3rd boss is defeated while it's firing the laser, the laser stays on screen while he dies.
When playing as Sonic in Death Egg 1 the objects that count down from 3 and then send you across some paths have a slightly different countdown tick. It's four low tones, instead of three low tones and one high tone.
When playing as Sonic in Death Egg 2 after the beat the boss was defeated the HUD turned green. This means that the game loaded Knuckles' 1P palette into the Knuckles CP palette slot.
When playing as Sonic at the credits. The Sonic 3 final credits roll, but the extended Sonic 3 & Knuckles medley is played. Also, the medley is longer than the credits, but the credits automatically restarts to the Sega screen a few seconds after "Try Again" appears.