In England certainly, but in Scotland presumably it started as Elizabeth R 71? Or perhaps Elizabeth I 71?
There’s certainly room for doubt in that system.
No, she was Elizabeth II in both Scotland and England. The convention was adopted, i forget when, it might have been for her, IIRC it was Churchill suggested it, that the monach would take the higher number of whichever country had had the nost of that name before. For example, Charles is Charles III because England had had two Charles before and Scotland none, but had he been called James he would have been James VIII, because Scotland has had seven Jameses already, which is more than England’s two.
I have no idea where Wales fits into this
You might as well decimalise time whilst you’re at it. Let us know how you get on,
The French tried that in Napoelon’s time, it didn’t go well. Apart from the fact that we have ten digits to count on a docimal number system makes so much more sense than a decimal one