Around Memorial Day.
I'm not sure, sorry
We were there last March and the pool was open. It was warm enough to swim then because It is heated and with the mild winter we have had it should be open now or very soon.
I don't have any idea, best to call and ask.
I'm not sure of the date on the outside pool. There is an indoor pool at the resort as well. I would think it would be early in spring since they do heat the outdoor pool as well. You can always call and speak with the front desk staff.
Get an answer from Greensprings Vacation Resort staff and past guests.