Sonic the Hedgehog Megamix (commonly shortened to Sonic Megamix) is a work-in-progress multiperson disassembly modification of the original Sonic the Hedgehog videogame for the Sega Mega Drive / Genesis, developed by Team Megamix and more recently moved to the Sega Mega-CD.
Here´s gameplay video by Razor & Zenon
Note – 1. Recommended Emulator for Sega Mega-CD
2. Click “Access to download” and it will direct you to a website for download.
3. Choose the version you want to download