Gift deed or release deed

Hi Experts, The property is on name of my mother and she is no more. We are three legal heirs of her property, namely husband, daughter and son equally. The Daughter do not want any share any she has given No objection certificate and based on society has transferred share certificate on my and father names. I want to take a loan against property, where bank is asking for a "Release Deed" from my sister for releasing her rights in favor of me and father? 1. Do I have to pay stamp duty on Release Deed? 2. What will be registration charges? 3. Is gift deed is better then release deed if stamp duty to pay? 4. Can govt demand later on release deed or any audit of same? Thanks in advance. Dharmendra S.