Alienation of property with GPA has been held illegal as per the law recently decided by the supreme court. One relinquishment deed of all properties will be enough no matter where in India they are situated but those should be mentioned in the deed. The easiest way to transfer any property is through gift deed but cheapest is by will which is not feasible as you and your sister on normal course out live the age of your mother. In case of more info feel free to reach out to me @ 9013429126. I provide 100% authentic paid advice on all legal matters.