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 1

3. 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 C

4. 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 Mode

C: (Normal Mode)Reverses Gravity. (Debug Mode)Toggles through the level\\\'s templates.

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.

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 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

Level Select (When Locked-On to Sonic 3)

Start a game and go to Angel Island Zone Act 1. Go to one of the swings that you hang from and grab on. While Sonic is swinging, press Left, Left, Left, Right, Right, Right, Up, Up, Up. You will hear a ring if you entered the code correctly. Pause the game and press A to take you back to the title screen. Press Down twice to find the newly unlocked Sound Test menu. Enter it, where you can play all of the sounds/music in the game and warp to any level.