builder unwilling to sign deed of sale

A) 11 year back I purchased apartment from a construction firm for Rs.22.65 lakh orally. Whereas The sale agreement was made for 23.65 lakhs (with a intention to avail loan amount to cover expenses of registration and stamp duty).The builder received 23 lakhs and returned 35000 honestly with a remark in writing refunding 35000 towards stamp duty. B.) The sale agreement contains these words....The possession will be handed over only upon receipt of full consideration. C) As agreed he has given possession of apartment and also a letter of possession. from last 11 years i am having the possession of said flat & i am using it. D) I approached builder for sale deed and he refused saying still the consideration is pending E) There was no communication by builder at any time for pending payment. F) To be frank there is nil payment is pending Kindly advice