Sonic 2

Level Select: At the main menu press UP, UP, UP, DOWN, DOWN, DOWN, LEFT, RIGHT, LEFT, RIGHT. Hold X and press START to access level select menu.

Debug Mode:Go to the sound test from the level select menu and play these tracks in order: 01, 09, 09, 04, 01, 00, 01, 08. This enables Debug mode. Holding X when selecting a level swaps objects from the level with the A button. Change objects with the B button, and copy and object with the X button. To reset the game, pause and press X.

All Emeralds: Play tracks in this order: 01, 06, 07, 07, 07, 02, 01, 06. To get all of the chaos emeralds.

Sonic 3 and Sonic and Knuckles

On Angel Island jump on the swinging vine near the bonus stage. While swinging press LEFT, LEFT, LEFT, RIGHT, RIGHT, RIGHT, UP, UP, UP. You should hear a ring chime. Sound Test will appear under the main menu.

Select Mushroom Hill Zone until you reach the ratchet machine. Hang from the machine and press LEFT, LEFT, LEFT, RIGHT, RIGHT, RIGHT, UP, UP, UP. Pause and press X again to reset. In level select , choose any level while holding X to use debug mode. Holding X when selecting a level swaps objects from the level with the A button. Change objects with the B button, and copy and object with the X button. To reset the game, pause and press X.