Sonic 3C Delta is likely a fan-made creation, potentially a ROM hack that involves modifications to the levels, gameplay, or other elements of Sonic the Hedgehog 3. The '3C' might refer to a version number, a modification that affects three specific aspects of the game, or an internal naming convention. Information on the actual development and creators would need to be sought out within fan game communities or online forums that specialize in Sonic related content.

Sonic 3C Delta

Sonic 3: D.A. Garden Edition