Transfer of immovable property

Hello,
 I have below questions:
1. What is the difference between succession certificate and relinquishment deed. What are the legal implications and disadvantage of both.


2. My father died recently leaving behind a floor in Delhi and plot in Noida. What would be the best and most suitable way to transfer these properties in the name of my mother. It is needed in order for her to become complete owner in order to able to sell if needed and also we can apply for mutation in relevant authority. Will the relinquishment deed be enough for it. If not, then what else is needed.

Also, my grandmother is alive. Does her consent also needed for the same.

Is it needed to get BOTH Succession certificate and relinquishment deed. Relinquishment deed alone will not suffice?

Thanks