I can't answer all the questions, but our old car had private plate, we were buying a new car last year. So we asked to take private plate off and put on to a retainer. I believe it's ten years on retainer, pay for another ten when that lapses or lose it. Alternatively pay to put it on another car.
DVLA then put original reg back on. We then sold the old car as if it never had a private plate.
We then bought the new car and transferred the retained private reg on to the new car and fully expect that if we decide to change cars we'll get the new car's old reg number back.
We paid once, and that was only to put on new car, as originally the plate came with fee already paid from DVLA when we bought the reg number. We never paid to transfer from old car to retainer.
