Could I take a classic/old phone(the kind with buttons) and switch its firmware with one from another brands and model? And would it work considering it doesn't have the same button layout? And if it is possible, what would it take?
Personally, I have never had such an idea, but if you already asked, my opinion is short and simple - no, even do not imagine how should it be possible.
But that's just my opinion and nothing more. (Sorry. I've been busy with electronics for over 40 years, but that doesn't seem to be enough to know more exactly.)