Sonic the Hedgehog 3 Cheats

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.

Make your way to the end of Act 1 of Hydrocity Zone (Zone 2). When facing the mini-boss, keep yourself underwater until the water warning music plays. Then jump out of the water.

The game should now be playing the mini-boss music from Sonic and Knuckles, which wasn't out at the time (the music was evidently included in Sonic 3 to make the backwards compatibility feature easier).

Enter the following code in any stage while Debug Mode is entered

Complete each achievement to get the allotted gamerscore.