Sonic 2 Beta 3? is a ROM hack created by Shadow05 which is supposed to recreate the prototype build seen between the time of the Simon Wai and Beta 4+ prototypes.
- Title cards display and use the Sonic 2 font (but not all are finished).
- Casino Night Zone is based of the version from Sonic 2 Delta; basically it's a much more complete version of the beta version of Casino Night.
- The 1UP theme, Oil Ocean, Hidden Palace and the invincibility theme plays are the replaced with the final versions of the tracks.
- Level select now displays Hidden Palace, Death Egg (which has one playable act), Sky Chase and Sky Fortress (note that Sky Chase and Sky Fortress are still empty).
- All zones except for Metropolis, Wood, Sky Chase, Sky Fortress and Genocide City can be completed.
- Spindash has been improved to be more like final version, except without dust.
- Genocide City plays the final boss music.
- You start in Emerald Hill.
- You can select 1 player and 2 player (but they aren't finished).
- The "Super Sonic Monitor" now gives you speed and invincibility.
- Emerald Hill, Hill Top and Neo Green Hill have object layouts similar to beta 4.
- The sounddriver is from Beta 4
- Casino Night Act 1 crashes the game.
- Game doesn't reset after the Green Hill (Emerald Hill) boss.
- Results gives you 99999900 points.