Sorry if this has been asked, could not find answer

I am currently renting a car from SAN, will return the car to SNA tomorrow(one-way rental is good place to burn free days) and I have another rental reserved at SNA tomorrow, can I keep the same car? since I luckily got a brand new Camero which I like.

Another question, is it possible to keep the car in National's location for 2-3 days during the rental? So I don't have to pay the parking fee near airport. Weekly rental is same price or even lower price than I rent 3-4 days and I don't want to change car that often..

Thank you for any input.