re3/revc are clean room reverse engineered projects, while gtav source we have is leaked proprietary code

Yeah, but probably not on GP, due to the copyright... so there will be people doing cash grab asset swaps with ad for every time you move a meter, and obviously malware creators on the internet

Yes, they can, but it doesn't mean they should, unless you wanna buy a new phone every few months, I'd know because I used to play Genshin on my phone.