Yes.
Yes it's possible. It's what we called "trade-in".
you can but its not always wise because you could end up buying the new car for more than what it is actually worth.
sure you can. but you will have to buy it back. why not just keep your old car and put a down payment on your new car because let's say the dealer gives you 5,000 for your old car as a downpayment on...
Yes. However, you are probably goping to have to cover some negative equity.