CVRP is a Post-Sale Rebate, so you can input it there. It’s essentially a mail-in rebate that you receive from CA after you take delivery, and it’s not something that involves the dealer.
As for your first and third question, it depends on the brand. What vehicle are you looking at?
San Diego is actually a test market right now for CVRP to be used at time of sale!
I have applied and I am waiting back to hear from them, it must be used via approved dealers in San Diego at time of sale, some good info for SD socal lease seekers