Sonic the Hedgehog 2 [Model G-4088]

* Stage Select : Under the 'Sound Test' menu, listen to sounds 19, 65, 09, and 17 in order; you'll hear a chime when you activate the last sound. Next, return to the title screen, highlight '1 Player', hold A and press Start to access the stage-select menu.

* Chaos Emeralds Cheat : At the Stage Select menu, highlight 'Sound Test' and listen to sounds 04, 01, 02, and 06 in order; you'll hear the fanfare that sounds when you get a Chaos Emerald. This code gives you all of the Chaos Emeralds; you can grab 50 rings and jump to change into Super Sonic. With this you'll be able to see the 'good' ending when you beat the game.

* Debug Mode : At the Stage Select menu, highlight 'Sound Test' and listen to sounds 01, 09, 09, 02, 01, 01, 02 and 04 in order; you'll hear a chime to confirm. Now highlight the name of any stage, hold the A button and press Start; don't release A until the stage begins. Screen coordinates will appear instead of a score and the number of objects displayed will appear instead of the time remaining. Use one of the following buttons sequences to enable the corresponding debug code...
Object transformation : Press B during game play to change Sonic/Tails into a game object.
1) Press A to change into a new object.
2) Press C to place an object on the screen.
3) Press B again to revert back to Sonic (Note : The type of object that may be selectable will vary from level to level).
Invincibility : Sonic/Tails is, by default, invincible in debug mode (Note : Sonic/Tails can still drown, be crushed, fall and die, etc. He is only invincible to enemy attacks).
Slow motion : Pause gameplay and hold B.
Restart : Pause gameplay and press A.
Frame advance : Pause gameplay and press C.