actual expense vs standard

I have a few rental properties. I have some questions for the auto expenses:

1) I bought a new car in 2021, how do I deduct the new car sales tax

2) the car 1 used for my rental expense for the past few years is totaled, so I will need to either use the car 2 we had or use the new car we bought. Can I stop using the car 1?

3) If I decide to use the new car, since the new car is used for the first year, is that true that I need to use standard mileage not the actual expenses.

4) If I decide to use car 2, I am not sure if I had used car 2 before, so can I use actual expense method for car 2?

5) How do I switch between standard mileage and actual expense methods?

 

Any help is greatly appreciated!

--Li