For more detailed pictures of the cart including pictures of all the pieces that make up the cart, check out:
Picture 1, Picture 2, Picture 3, Picture 4, and Picture 5.
Download the ROM which includes a copy of the save file from the prototype cart below:
[Sonic Advance Prototype + Save File]
Differences between the prototype and final:
Game freezes in certain areas of the level (Secret Base, Casino Paradise)
Spinning Tubes either don't function right or don't work at all (Secret Base, Casino Paradise, Egg Rocket, Cosmic Angel)
Other interesting key notes about this prototype:
The Tiny Chao Garden contains a semi raised Chao name Dooogy.
The information on the header doesn't match what is shown in the USA, EUR, JAP final.
The prototype cart has a complete save file (all emeralds acquired/all levels accessible for every character).
Using Hex Workshop, the save file appears to be slightly different to one VisualBoyAdvance creates in way that's very amusing (you'll see what I mean).
Now there may potentially be a lot more to this build than meets the eye. For starters, I've done a file comparison between the prototype and the final version (all three regions) using Hex Workshop and there are some differences. However, I don't know what that translate to. Perhaps someone can look further into it. I do have some example pictures of some of the stuff I found however, I want you folks to have a go at this to see what you can find and whether there is anything else I might have missed or didn't know was there.
I've done several dumps of this to make sure there were no bad dumps. Made sure what I was using to dump the game was functioning correctly. Hopefully this ROM didn't fall victim to being uploaded into the cart incorrectly back in the day, bit rot, or anything else (like the cart being non-functional at first due to the hardware which I managed to fix) that might have left the ROM in this state. If not, this is the real deal then.
There is also a very interesting story in regards this prototype which I'll be happy to share you with at some point. Hopefully I might have more to enlighten you with as well at some point. Enjoy!