As this was a remake instead of an emulated port, new features were added. The new features were similar to the previous 16-bit game remasters. The Taxman confirmed that no features from Sonic 2 would be excluded.
New features included a remastered soundtrack, the game running at 60 fps during normal and special stages,, a remade version of the lost beta level Hidden Palace Zone, and an eighth Special Stage.
Start a "No Save" game and choose a character. Once the Sega logo appears, tap the letters S-E-G-A in that order. If done correctly, a chime will sound. Then on the main screen tap and hold with two fingers. You will then be taken to the level select screen.
Tails/Miles Name Change
If you wish to replace the appearances in-game of the name "Tails" to "Miles", tap the letters A-G-E-S in that order when the Sega logo appears. If done correctly, a chime will sound. This can be done on both a saved game and No Save Mode game.
Game Configuration Menu
Play the sounds 00, 00, 00 in the sound test to bring up the game config menu.
You can choose between Sonic alone, Sonic and Tails, Tails alone, Knuckles and Tails, or Knuckles alone.
You can also choose between Sonic 2's monitors, Sonic 3's monitors, or hidden (2 player) versions of either of those monitor sets.
Warning: The "hidden" set may randomly generate the monitors. More testing required.
Flight and Air Cap can also be toggled.
Play sounds 01, 09, 09, 02, 01, 01, 02, 04 in the sound test then select a level.
The debug mode numbers here, like Sonic 1, are the North American release date: 1992/11/24
To enter debug mode tap in the upper left hand corner of the screen. A minus sign (-) and a plus sign (+) will appear. These can be used for navigating back and forth through the debug items. To exit the level and return to the level select screen, tap the upper right hand corner of the screen. To enter normal play again tap the upper left hand corner of the screen.
Play sounds 04, 01, 02, 06 in the sound test. You should hear the sound of an emerald being collected. You will now have all seven Chaos Emeralds. Possibly inspired by Genesis 41:26: ""The seven good kine are seven years; and the seven good ears are seven years: the dream is one."
Proto Palace Zone
Play sounds 01, 09, 09, 02, 01, 01, 02, 04 in the sound test to enable debug mode. You must do this or it will not work.
Then play the sounds 03, 03, 03, 0B, 10, 10, 10, 04, then select Hidden Palace Zone.
This is the original version of Hidden Palace Zone from the Simon Wai and Nick Arcade prototypes. Its background music is track #10 and at the end of the stage the emerald will send you back to the level select screen.
For reference, the themes used in the code are, in order, Hidden Palace (the final version of the level), Oil Ocean, (the level after Hidden Palace), Proto Palace (the level you're opening), and Mystic Cave (the level with the Hidden Palace entrance).
If you die in Proto Palace Zone, you will not be sent back to the level select nor reappear in Proto Palace Zone. Instead, the game will load Hidden Palace Zone.
"Clearing" this zone by placing a signpost or a capsule in Debug Mode will load Oil Ocean Zone.