You can get a new phone if your old one breaks. They will probally replace it with the same model as your old one. Depending on the terms of the contract, you might be able to buy a whole new phone. It depends on the phone company.
Yes you can. I know Verizon lets you trade phones to a newer phone every 2 years. If you do it sooner they charge you the full price. If you wait they give a discount. The other cell phone companies...