Select "Sonic & Knuckles", choose any character, and play "Angel Island". Jump and hang on a swinging vine. Then, press [Left], [Left], [Left], [Right], [Right], [Right], [Up], [Up], [Up]. If you entered the code correctly, you will hear a sound.
Sound test
Enable the "Level select" code. Then, restart the game using the option under the "File" menu. Now at the title screen, press [Down], [Down].
Screen capture
While playing the game, press [F9] to save an image of the current screen in the game directory.
Super Sonic
Collect all seven emeralds, then accumulate fifty rings or a single bonus. Then, quickly jump twice in succession.
Sonic special stages
Enter the following codes on the special stage screen.