Topic: Gameboy pocket and Gameboy colour and advance SP

Is this the correct forum for any questions for all of the above
I am a novice
Ty

Thank you
I will own a pocket soon and hopefully in time a colour and SP advance
I am
I wanted to know the best place to get genuine games please
I do know of some decent sellers on eBay but they don’t have many games and it seems original cartridges have numbers on them but these can be faked which make it difficult to know truth !?
Is it correct that cartridges for pocket and colour are same but advance uses all of them ( can’t put advance into pocket or colour )