What happens to aisle seat payments if I get on an earlier flight as standby.

A few questions…..1. If I paid for economy plus seat choices on flight later in the day, but found I will be able to fly earlier, do they refund the money paid for aisle seats, or better yet, allow me to get aisle seats on the earlier flight?

2. Does it matter if I do this as standby or actually change the flights online?

3. If somebody was assigned the last aisle seat without paying on the earlier flight, would they put me in the aisle seat since I had paid for an aisle seat later in the day (this question assumes question one is answered affirmatively)?

4. Since I may even be able to fly the day before, how would the seat payments work in that case?