As far as I'm aware- if it's called an ARM CPU it's either the v7 or v8 instruction set with the possibility of extra instructions (changes to ARM die) or a tightly integrated coprocessor (via AXI bus, adjacent to the ARM silicon on the same substrate).

There are different Coretex series that optimize for different things- A and X for applications (phones, cloud compute, SBCs, desktops and laptops), M for microcontrollers, and R for realtime.

This doesn't apply if the company has an ARM founder and/or architecture license. (I think that's what they're called) Eg- Apple and their M series SOCs are not Coretex cores, but share the base instruction set- but only if Apple wants it to.

Yup, Amazon supports the 6.11? kernel on aarch64. Most toolchains if you target linux aarch64 static they, they will produce executables that will run on Amazon Linux aarch64 and Android, set-top boxes with 64-bit chips and Linux 3+ it's surprising how many devices a static aarch64 ELF will run on.

Yes, think AMD vs Intel. Same x86 target but built differently under the hood with potential to optimize for certain uses over others.