I had some free time to finish researching the Vectorman/2 prototypes (started around March of last year). There is more to be seen in them, though. My main objective was to get the button codes to explore the game quickly.

Here are some videos I uploaded on my YouTube channel for Vectorman/2:

Vectorman:
http://www.youtube.com/watch?v=Rf5jFdoMpds
http://www.youtube.com/watch?v=hRBpZ6uFfec
http://www.youtube.com/watch?v=ywlQBYvs49Q

Vectorman 2:
http://www.youtube.com/watch?v=KStn-G4Czhk

-- Vectorman (Prototypes) --

Some pics I took of the oldest prototype to my knowledge (the one with the "Rocket" level):
http://i56.tinypic.com/29y1e1u.jpg
http://i53.tinypic.com/11cb3mg.jpg

All of the codes for the prototypes (the prototypes Drx released use the retail version codes):

Options Menu: Press Z on a 6 button controller during gameplay.

Cursor Mode: Pause the game and press C, A, Left(2), A, C, A, B. Repeat the code to disable it.

Map Coordinates 1: Pause the game and press C(2), A. Repeat the code to disable it.

Map Coordinates 2: Pause the game and press C(2), B. Repeat the code to disable it.

Map Coordinates 3: Pause the game and press C(3). Repeat the code to disable it.

Full Health: Pause the game and press A, B, Right, A, C, A, Down, A, B, Right. A.

Collision Detection (Enemies): Pause the game and press X(3) on a 6 button controller.

Collision Detection (Vectorman): Pause the game and press Y(3) on a 6 button controller.

Debug Menu: Press Down, Up, B, A at the options screen. Repeat the code to disable it.

Slow Motion: Pause the game and press Down, Right, A, C, Up, Left, A. The game will slow down when Vectorman is hit. Repeat the code to disable it.

View Credits: Press C, A, B, A, Left at the options screen. This is useless since there is already an option for it.

Level Skip: Pause the game and press A, B, C. Unpause the game after.

Unknown Meter: Pause the game and press A, Left, A, B, A, Mode, A on a 6 button controller. A meter will appear under your score. I think it has something to do with the VRAM. Note: This will work in the retail version.

Unknown Cheat (disabled): Press B, Up, B(2), A at the options screen. This code works in the retail version (the 'score multiplier' sound effect will be heard), but I have no idea what it does. Repeat the code to disable it. The PAR (Pro Action Replay) code is FFE810:0001 (retail version). Enable it at the title screen to avoid conflicts with the Sega intro.

Unknown Cheat 2 (disabled?): Press C, A, Left(2), A, B, A, Down, B, A, B, Y, Down, Up, Mode, B (spells CALL A BAD BABY DUMB) on a 6 button controller. Note: This code is present in the retail version. I have entered this code everywhere with no confirmation of it doing anything.

-- Vectorman 2 (Prototype) --

These pics are from Vectorman 2 (Prototype - Aug 15, 1996):
http://i54.tinypic.com/moabp.jpg

I don't recall seeing this weapon in the retail version:
http://i53.tinypic.com/33ngia1.jpg

No need to enter the weapon code X times like the retail:
http://i56.tinypic.com/2maaeg.jpg

These codes will also work for the August 16 and 19 builds. The builds from August 26 through the 28 use the retail version cheats.

Level Select: Press X on a 6 button controller at the options screen, or during gameplay. You can also view the credits and press Start.

Weapon Select, Infinite Ammo, and Full Health: Press Y on a 6 button controller during gameplay. The weapons cycle in this order: M Ball, Rapid Laser Beam, Energy Shot, Super Shot, Overkill, Pulse Beam, Tick Punch, G Shot, Fireball and Shield. Note: Most of these are missing in the August 16 and 19 builds. 

Cursor Mode: Pause the game and press C, A, Left(2), A, C, A, B. Repeat the code to disable it.

Map Coordinates 1: Pause the game and press B, A, Left(2). Repeat the code to disable it.

Map Coordinates 2: Pause the game and press Left, Up, A, Up. Repeat the code to disable it.

Map Coordinates 3: Pause the game and press B, A, Left, Down. Repeat the code to disable it.

Full Health: Pause the game and press A, B, Right, A, C, A, Down, A, B, Right, A.

Slow Motion: Pause the game and press Down, Right, A, C, Up, Left, A. The game will slow down when Vectorman is hit. Repeat the code to disable it.

Unknown Meter: Pause the game and press A, Left, A, B, A, Mode, A on a 6 button controller. A meter will appear under your score. I think this meter has something to do with the VRAM.

Restart Level: Pause the game and press Left(2), A, Mode, A on a 6 button controller.

Sample/Keith's Test level codes:

Cursor Mode (Version 2): Press Z on a 6 button controller during gameplay. You can move anywhere in the level. Press Z to place Vectorman.

Level Editor: Press Z on a 6 button controller during gameplay. Then, press the B button to scroll through the sprites, and A to insert them.

These are leftovers from Vectorman:

Unknown Cheat (disabled): Press B, Up, B(2), A at the options screen. You'll hear the 'score multiplier' SFX to know it's enabled. I have no idea what it does. Repeat the code to disable it. The PAR (Pro Action Replay) code is FFE810:0001 (retail version). Enable it at the title screen to avoid conflicts with the Sega intro.

Unknown Cheat 2 (disabled?): Press C, A, Left(2), A, B, A, Down, B, A, B, Y, Down, Up, Mode, B (spells CALL A BAD BABY DUMB) on a 6 button controller. The Vectorman 2 version of this code is C, Right, Y, B, A, B, Y, C, Right, Y (spells CRY BABY CRY) on a 6 button controller. I have entered this code everywhere with no confirmation of it doing anything.

Unknown Cheat 3 (disabled): Press A, B(2), A, Down, A, B(2), A. This was the debug menu code for Vectorman.