Mystery?

I've seen some early photos of some of the Japanese Bandai solar games that have never actually been released! Are they prototypes? Here are some pictures:

A small version of Daidassou (never released in that format!):



A small version of Nazo No Chinbotsusen (never released in that format!):



A small version of Gekisen U-Boat (released in that format outside Japan as Sub Attack, Sub Patrol and U-Boat):



A small version of Kyofu No Mujintou (release in that format outside Japan as Shark Island):



On the other hand I have not seen any trace of an existing large version of Tengoku & Jigoku (Escape from the Devil's Doom)...

If anyone has any information I would be very interested.

Links:
- Missing versions?