Just had a playthrough of Beta 4 today and found a few differences that I didn't see documented. CNZ boss: Robotnik's electricity is a sort of red colour, as opposed to blue in the final. MCZ act 2, there are 3 pendulums near the start instead of the 2 in the final. Robotnik's drills have flashing lights on the side, probably sharing the pallette of the swinging lanterns. And finally, the OOZ boss' lasers/flames are a darker blue than the final.