Sonic World 64 - First is a hypothetical ROM hack, a fan-made project created by individual ROM hackers and not an official release. The name suggests a game with a Sonic theme, designed for the Nintendo 64, and is likely a first iteration of the project.  Gameplay would have elements from Sonic games, but adapted to the base game's mechanics.   The distribution of this game would happen through ROM hacking communities.

Sonic World 64 - First

Sonic in Ocarina of Time