Q1: Will Federal refund the difference or they refund the amount of my first tax return and withdraw the due from my bank account later in May?
you didn't make it clear but it appears you chose to make e-payments
good question. since you can withdraw the May payment, the IRS may only refund the excess without the May payment and later refund the May payment
Q2: TurboTax asks me to print 525-TV and mail with my payment however I chose to pay from my bank account, so is it correct that I just mail 525-TV or I don't need to do anything at this part?
the 525 is to accompany a mailed-in payment. since you chose to e-pay do not mail it in otherwise they may send a notice asking for the payment
