Sonic the Hedgehog (lost build of cancelled SEGA CD port of SEGA Genesis platformer; 1992)
From The Lost Media Wiki
Sonic 1 CD is a port of Sonic 1 to the Sega CD to be a definitive version of Playing Sonic the Hedgehog 1, It was showcased at the Consumer Electronic Show(Or CES) to show the power of the Sega CD. It was also teased in issue #11 of Mega Play. The reason that it might have been cancelled was in favor of Sonic CD being the Main Sonic title on the CD.
Only some footage of the game exist online and a handfull of screenshots, so it remains lost. But a Fan Remake of Sonic 1 to the CD does exist made by Sonic retro user " HCKTROX".But the original build is likely lost in time