

I agree, but the instruction set (what you called a chip architecture, which isn’t wrong at all but potentially confusable with microarchitecture which is how you implement the instruction set architecture) has nothing to do with this. Though Apple does have the ability to make their own instruction set if they want, they and (mainstream) Android currently use ARM, which is also an open standard.
Not sure what you mean. Isn’t the base just GNU/Linux?