Any licenced FFL dealer. So long as it's not stolen and reported as such, you can sell it.
357 is not evenly divisible by any number, except 1, 3, 7, 17, 119, and 357.
You can't. No paperwork, no proof.
Any .357 Magnum revolver (this does not apply to automatics or any other type of firearm) can fire .357 Magnum and .38 Special cartridges.
Yes, along with your grandfathers' sisters, if any.
No. Dirt bikes are usually not road registered (although it can be done) so there is no need for any paperwork to sell a dirt bike.
Any .38 ammo can be safly fired in a .357. +P .38 loads do not exceed .357 pressures.
No.
Yes, you sure do. If you are raising animals to sell as meat, there is a mountain of paperwork you will have to wade through first.
No
you do not need to bring any special paperwork if you are buying a car from a car auction. the only proof you will need is the paperwork after to buy the car to get insurance and the titles switched in your name.
Every number is divisible by any non-zero number. Furthermore, 357 is evenly divisible by 3.
Yes you would. He/she could become yours