"The bag is on the car."
Translation:A táska az autón van.
Your sentence means something else. The DL sentence means 'on' the car; your sentence means 'in' the car.
In some sentences, yes, but here you would not want to. In Hungarian, you want to place the newest or most interesting information (it is on the car!) before the verb.
Why does it require "van" while in some of the prievous excercises "to be" in the third person was marked ad wrong?