Bonus game trick
Put a game other than Sonic 2 or 3 in the top of the Sonic & Knuckles cartridge. Then, when it shows the picture of the trio and the message at the top, press A, B, and C simultaneously to play Bonus Games.
Debug Mode (Locked-On to Sonic 3)
1. Enter the level select code by pressing Left, Left, Left, Right, Right, Right, Up, Up, Up on the swinging vines in Angel Island. Press Start then A to restart the game.2. Enter the Level Select area (Sound Test) and select Mushroom Hill Zone Act 13. From here, grab on to the pully levers and press Left, Left, Left, Right, Right, Right, Up, Up, Up. Press Start then A. From this point forward, push and hold down buttons A, B, and C4. Enter Sound Test again.5. Select a stage of your choice. Once the Zone and Act title dissapear, you may release A, B, and C. There are a few differences in button layout now.A: (Normal Mode)Makes Sonic jump normally. (Debug Mode)Duplicates the selected item.B: Toggles between Normal Mode and Debug ModeC: (Normal Mode)Reverses Gravity. (Debug Mode)Toggles through the level\\\'s templates.
Debug mode and all Emeralds (locked-on to Sonic 2)
First activate and go to the Stage Select. Play the tracks in Sound Test with button B in this order:
01 09 09 04 01 00 01 08
This enables the Debug code, you should hear a ring chime if the code is entered correctly. start the selected level with A+start.
To get all 7 Chaos Emeralds, input this code the same way:
01 06 07 07 07 02 01 06
You should hear the Emerald chime. note: this code may not work without the Debug code
Debug mode in Sonic 3 and Knuckles
While playing sonic 3 and knuckles press Left, Left, Left, Right, Right, Right, Up, Up, Up in the mushroom hill zone, while on one of the pully things. (Just like level select in normal Sonic and Knuckles.) I think you have to do the level select code first.
Debug mode
Left, Left, Left, Right, Right, Right, Up, Up, Up