>The theory is that it will be used to settle inter-bank transactions once it is widely adopted by institutions.
Banks have absolutely not need of a proof of work scheme like Bitcoin, them switching to a system with the power requirements of BTC seems highly unlikely.
There can be no such thing as an ARM compatible instruction set that is not an ARM instruction set. Either it supports the necessary instructions then it is an ARM instruction (possibly super)set or it doesn't then it's incompatible.
Depends, performance wise it should be able to compete with or even outperform x86 in many areas. A big problem until now was cross compatibility regarding peripherals, which complicates running a common OS on ARM chips from different vendors. There is currently a standardization effort (Arm SystemReady SR) that might help with that issue though.
With AMD you have the clear competitors Intel and Nvidia with their respective market share, revenue and valuation.
There was a real world reason for their low valuation (Bulldozer) and a real world reason for there stock to recover (Zen). Intel had been stagnant for years and their 10nm was obviously not working. With AMD's and Jim Keller's track record there was a reasonable case for them managing to catch up and their stock to rise accordingly. If those are meme arguments the whole market is a meme.
Banks have absolutely not need of a proof of work scheme like Bitcoin, them switching to a system with the power requirements of BTC seems highly unlikely.