Cowboy Classic Sonic Y 64 is likely a fan-made ROM hack or homebrew title for the Nintendo 64. It is a very obscure title, and it appears to blend elements of the classic Sonic the Hedgehog gameplay with a Western or cowboy theme. Without more information, it's impossible to provide specifics about its gameplay, developer, or release.  This title is almost certainly not an officially licensed or released game.

Cowboy Classic Sonic Y 64

Conker's Bad Fur Day Uncensored