Do not know the answer for your first 2 questions.

However, there is no tax as a gift donee--for gift, only the person who give the money(donor) pay the tax.

http://www.irs.gov/businesses/small/article/0,,id=108139,00.html

Since you are using the money to buy a house, if you are planning to get mortgage, you better get a statement from your parents to claim that it is a gift. Otherwise, the bank may not give you the loan.