Sonic Advance International (and also MOST Mods) is based on the Chinese game version that I found on this website : https://archive.org/details/1.0.0_202310
The game version is indeed the cracked version that you're talking about. However, I managed to remove the pop-ups and made this mod the full-game version by default. I may not be an expert at programming, but I do have some experience.
As for what you can help for my game mod, I'm mostly looking for programmers who has experience with Java/Smali programming for further modding. However, you can help me for making a Traditional Chinese version if you want.