Comme tout le monde le sait déjà, cette version tourne trop vite sur les PC modernes mais grâce à un petit changement de fichier c'est résolu (ça et le débug mod).

Debug Functions via S3K.ini

• Though you can enter the debug menu code in-game, you cannot use any object placement functions as controls are limited to four directions and a single key for jumping.
• However, you can properly enable it by creating a file named "S3K.ini" in your C:\WINDOWS directory (where C:\ is the main partition used for Windows) and typing the following into the file:

[Debug]
DebugMode=1
EnableFrameDrop=1
MukaiDropFrame=0
ShowFrameCount=0
EnableFrameCapture=1
UseModeX=1
NoSoundEffect=0
CDCheckEnable=1
SonicGameMode=0
BGMMode=2
GameMode=0
LangMode=0

Il faut remplacer le "0" dans Enable Frame Drop par un "1"

Level Select:

• Go to Angel Island 1, grab onto a swinging vine, and press Left, Left, Left, Right, Right, Right, Up, Up, Up. A ring sound will play if you did it right.
• Press Alt + R to reset the game and from the title screen press Up to reveal "SOUND TEST" and press Enter. Press Numpad 3 to change your character.
• The method of unlocking the level select in Sonic 3 & Knuckles apparently works in Sonic 3 alone (a good thing, too, considering it's a lot easier to unlock this way) though debug mode won't be unlocked along with it and you can select any Sonic 3 zone as usual (but not Flying Battery, Mushroom Valley, Sandopolis, or Bonus).
• In Sonic & Knuckles, this method must be done on the pulley lifts in Mushroom Hill Zone.

Source: The Cutting Room Floor https://tcrf.net/Sonic_%26_Knuckles_Collection