-THE OTHER ZONES?-
In Sonic CD beta you are restricted to play three zones. When you finish act 3 of Tidal Tempest, the game shows you a "Coming Soon" screen. However, if you look on the CD directory, you will notice that there are more level files than you normally play. Each level or menu is a separate module with the file extension *.mmd. I accessed the other zones by switching the file data. However, the easier way is to do the level select cheat. Thanks to ICEknight of http://go.to/sonicdatabase who found the cheats.
To get the level select screen, do the following
-Go to the title screen
-Press start on player 2's control pad
-The start game and time attack options should stop blinking
-Press Start on player 1's control pad to enter the level select
To access debug mode, simply press start on player 2's control pad. The Score and Time panels should change to hex numerals
2 PLAYER COOPERATIVE MODE
Press the 2P Start, A, B or C button when you're playing a game, and another Sonic will appear, which can be controlled with the second Pad.
The levels after Tidal Tempest are more beta-esque. In most cases They have no enemies or rings and the level designs are different in some acts. I remember someone having a theory about the pictures in the time attack representing what the levels looked like in earlier version. I can say that this theory is spot on (especially with Quartz Quadrant).
Quartz Quadrant-Act 2
The stalagmites are in front of the foreground like in the time attack picture. There is also a chained platform that doesn't appear in this area. In the second picture the platforms look different to the ones in the final. Notice how they are rough/rocky/spiky at the bottom compared with a flat bottom in the final.
Stardust Speedway - Act 1
The level design is slightly different with little or no sprites at all. Notice the Eggman statue in the background.
Metallic Madness - Act 2
The level design in this act is vastly different from the final one. In the first picture you will notice that there are miniature spinning wheels as well as the large ones. In the second picture there is the large spiky ball. This is slightly larger than the final one as well as being shaded correctly.