Sa & gpa validity

No it is not possible. The gpa ends on deaht of eithere party. 

I agree with what Ld. Mr. Rao just said . GPA ends with the person. however there is also an agreement to sell here. Agreement to sell + GPA + Will + Reciept are normally employed to sell property in order to evade the stamp duty leviable on Sale Deeds. It has to be understood that 'agreement to sell' is basically a contract whereby two people agree to carry out the sale later or subject to some condition. Since you have the Agreement to Sell. You cannot go in for mutation directly as it does not create a right/title in your favour. What you can do is you can go in for Specific Performance of this agreement and oblige the other party to perform the Sale Deed. Since this is not a personal contract that could have been performed only by the deceased father. You can seek the Specific Performacne as you are his representative in the eyes of law. Furthermore I would advise you to look if there are other documents supporting your title or not. 

However it is to be noted that if the transaction in question was made before 2001 - your right to possess the property is indeafisible and you need not worry about the same. As S.53A of the TPA, also known as part performance - would help you retain possession if some person challenges your right to be there.

Feel free to seek any clarifications !