I cant answer 1 & 2 because i don't know.
3.Charges were 500 last time i checked here in karachi.
4.Validity is 1 year.
5.Get photocopies of your NIC, Valid Driving License and Passport (first page and Visa). Keep the originals with you that you may have to produce them on request. Along with them, you will need two(2) 1"x1" size photographs.
6.Its fine if you rent a car in dubai but make sure it has navigation so you wont have problems while going places.