WILL/Partition Deed/ Relinquishment Deed

I need your suggestion on below: My father expired without writing a WILL. My family contains of 5 members-Myself, my mother, my grand mother and sisters[Married]. Excluding my grandmother, we four of us has made a partition deed. Now, when we were trying to sell the property, we recently came to know that even my grand mother is also a legal heir to my father. As a grandson, I am taking care of my grandmother and she is willing to give her share/right to me. Please answer my following questions. 1. Can we still go for a relinquishment after partition[grand mother not included in the partition document] 2. Can my grandmother transfer her rights alone to me excluding the remaining 3 or it can be done to four of us only? 3. At the time of relinquishment, Do my sisters and mother needs to be present at Sub registrar office ? or myself and my grandmother are enough? 4.Is this Relinquishment deed a permanent solution for selling the properly if not please advise what best can be done here[ like getting a WILL from my grand mother etc] PS: Actually this is my friends issue and I just replaced him with me to make the context clear. I appreciate your quick response on this