Sonic 4 in 1 is a homebrew game for the Sega Genesis. It's not an official title from Sega but rather an independent creation featuring multiple mini-games or levels in a single compilation. The game's exact content varies, and details depend on the version, but generally, it attempts to present players with multiple smaller experiences, themed around the Sonic universe.  These compilations are made by fans and represent unofficial additions to the Sonic game library.

Sonic 4 in 1

Sonic 3D Blast (USA) (Beta)