As your Rover is discounted, I would imagine from the discounted Anytime fare, or even the Off-Peak Single should one exist as a Rover is time-restricted.
It would be the difference between the discounted standard class fare and the undiscounted 1st class fare.
Yes, it does, but not sure how the value is calculated.
That must be open to abuse.
Buy an ALR, get back, find trains that were delayed, say you were on them and get some money back!