This is a really early beta of Sonic 2 which can be found HERE: http://www.mediafire.com/?g5nyj5jwjzn . This beta features only 1 complete zone - Emerald Hill zone. It is the only zone that will play by simply pressing START on the title screen. However, if you use level select (up down down down down up), you can access some of the original zones of Sonic 1. I also used Debug Mode (up C down C down C down C down C up C) The level select will show only Sonic 1 zones. One you can access is a very glitchy Green Hill Zone. The graphics are messed up and the physics and hit detection are also flawed. You can fall through the Ground. There are some game genie codes that (mostly) fix this. Those codes are (you must use them all at once):
Even though most of the physics are fixed, some things are still messed up. You cannot run around loops, and the platforms that fall (they stick out of the edge of a platform) sometimes act wierd (you can fall through them). These codes mess up the physics in all of the Sonic 2 Levels.
Also, here is the list of what levels are on the Sonic 2 Beta.
Green Hill Zone=Green Hill Zone (with messed up graphics and physics. Marble Zone=Chemical Plant Zone. Spring Yard Zone=Hidden Palace Zone. Labyrinth Zone=A void in which you (and Tails) fall to your death. Star Light Zone=Emerald Hill Zone. Scrap Brain Zone=Hill Top Zone. Final Zone=A level of Hill Top Zone that freezes when you go far enough to the right (to the first loop). Special Stage=Nothing. It freezes up the game.