can I get a temporary plate number
If I purchase a car from a dealer in cash they can give me a temporary plate
Most dealerships can, but I would check with them. They still need to fill out all the same paperwork in your name as you would if you went into the license bureau yourself. Again check with the specific dealer if they can provide temp tags.
That would depend on the state you are in. Some states have a temporary registration that is stuck to a window. What ever you buy the dealer will make sure you are legal before you leave the car lot.
Any professional dealer will ensure you have what you need to drive legally on the road. If temp tags are used in your area, you should get them.