1. Yes the borrower has 20 days, and therefore it is not the bank's asset until that time has passed.
Unless you are using "strict foreclosure", which I do not recommend because of it many limitations, the vehicle is never the bank's asset unless the bank purchases the vehicle at the foreclosure sale, which, in some situations, may not be wise.
The loan is a foreclosed loan once you repossess the collateral. When you recognize any loss in the value of the loan asset has more to do with general accounting principles. I would recognize the cost of collection and foreclosure as a period expense and not charge it to the loan loss reserve.
I would not charge any loss to the reserve until the debtor's time to cure has lapsed and the collateral has been sold. The amount of the loss is then an amount certain.
The amount of time you have to sell the vehicle is controlled by Article 9 (part 6 default).