A prototype version of Shin Megami Tensei: Devil Children – Book of Ice has been released for archiving purposes recently by Reddit user DurandalJoyeuse. The prototype contents come from one of the three only known prototype cartridges of the game known to be in existence.
It seems that the prototype differs from the full game slightly, mainly in color palettes. There are other differences that pop up here and there.
Shin Megami Tensei: Devil Children was a series of spinoff RPGs that followed in the trend of the Pokémon series while retaining the core characteristics of the series. The first pair of games released on the Game Boy Color, and Book of Fire and Book of Ice were the last main games in that branch of spinoffs, and were released for GBA in 2003.
You can find the prototype at Archive.org here.
Shin Megami Tensei: Devil Children – Book of Ice was released for Game Boy Advance.