Do you have rental cars that can be dropped off in another state? ex. If I fly in to Boise and decide to rent a car to drive back to Cali is that available ?

You need to call the airport location to see if they have a Cali car you can drive back. Sometimes you can get a pretty good deal if they have a Cali car stuck in boise and you are willing to drive it back!

I'm pretty sure the license plate of a rental doesn't matter. They give you the option to drop the car off at a different location than the one you picked it up at.