Sonic the Hedgehog 2 (Simon Wai Prototype)

The Sonic the Hedgehog 2 "Simon Wai" Prototype is an early prototype of Sonic the Hedgehog 2 (16-bit), it's more complete/advanced than the Nick Arcade Prototype but is still very different from the final game.

Origins
The ROM image was discovered by Simon Wai on a Chinese Geocities page in 1998 and was the first prototype discovered and until 2008 was simply referred to as "Sonic 2 Beta".

The origins of the ROM itself likely came from a demonstration cart stolen from a NYC toy fair in 1992, then dumped online.

Various Differences

 * The SEGA logo only appears after you finish all the levels/get a game over/let the demo play. The sound itself is at a higher pitch.
 * It's using the Nick Arcade title screen and would continue to be seen until Beta 5 where its replaced with the final game's title screen.
 * The level select is enabled by default, just hold A and press Start.
 * Night Mode is enabled by default, just hold C on the level select.
 * To enable Debug press C, C, Up, Down, Down, Up, then hold A and press Start.
 * There are no checkpoints in the level, but they're playable in Debug Mode but they don't function yet.
 * It still uses Sonic 1's Serial Number, This means if locked on to Sonic & Knuckles it'll enable the Blue Spheres Minigame.
 * Many layouts are different, but almost none of them have badniks.
 * Hidden Palace is still playable and mostly had minor changes from Nick Arcade.
 * Genocide City and Death Egg are empty.
 * In Death Egg, if you fall to your death the sound driver cuts off all sound due to unknown reasons. Music for this stage is in ROM but strangely not in the music playlist.