Sonic the Hedgehog 3

Technically, there is no code in the sound test for that. You may be thinking about Sonic 2. However, if you want to GET to the sound test to start Debug Mode, simply beat the game first so you have access for all of the levels. Then, go to Angel Island, jump on one of those swinging vine things, and push L,L,L,R,R,R,U,U,U (or is it R,R,R,L,L,L,U,U,U? I can't remember) after that, you should hear a ring-collecting sound. Pause, and push the A button. It should return you to the title screen. Then enter Mushroom hill zone. Go to one of those things that you have to push down to go up. Again push L,L,L,R,R,R,U,U,U, the same code used on the vine thing. Again, ring sound. After that, pause, push A, then go to anyone of the levels while holding down A (I recommend pushing START to select the level and then immediately hold down A. Pushing A, then START returns you to the title screen, by the way. The level should come up paused, simply un-pause). Then you should get Debug Mode. This, in my opinion, is the easier and less frustrating method opposed to the title screen code.