-The SEGA logo background features a picture Newtrogic High Zone. This would end up being cut out completely from the game, but does make an appearance in the manual.

-The title screen is missing the characters, the background is higher up and you can cycle through game modes at the bottom.

-The options menu is a black screen with a few numbers on it, and acts as a sound test.

-The main menu has a stage select option on it.

-Inside said stage select, there is a choice of eight different times of day for a level, the final version only has four!

-The data load screen has some glitchy text.

-The level title cards call Heavy "Heaby", but more interestingly is the fact that the cards refer to the game as "Knuckles' Ring Star".

-Debug mode is always on. Press start to pause the game, then use the control pad to move around a level.

-There are a huge amount of differences in the levels, some of which -such as most of the Speed Slider levels -don't work yet.

-The special stage consists of a short, looping level which is quite obviously a very early work in progress. There are no blue spheres to collect, and you can only exit it by falling or running out of rings.

-The title screen has been updated. It doesn't match the final version, but the characters now appear. Beneath the Chaotix logo it states "FEATURING ESPIO THE CHAMELEON", if you have your emulator's region set to USA.

-The times of day has been reduced from eight to four.

-The special stage has been slightly updated, but you still can't actually collect any blue spheres.

-Knuckles has different sprites for climbing, and you must hold the jump button to climb. Letting go will make Knuckles jump off.

-Level title cards now have the word "Chaotix" on them instead of "Knuckles' Ring Star".

-Some of the special stage graphics have been updated.

-Copyright info has been added to the title screen.

-Further updates to the special stages.

-Chaos rings are called "Holy Rings".

-The SEGA logo now has a different background.

-When the SEGA logo appears, a sound is played.

-The intro is now much closer to what the final version has.

-The title screen now has "FEATURING KNUCKLES THE ECHIDNA" no matter what region your emulator is set on.

-The special stage maps are now the same as the final version.

There are also prototypes available for the 8th, 9th, 10th, 13th, 14th and 16th of February. I haven't played them much but from what I've read, they aren't very interesting. There's also another one for the 19th of January.