Clarification regarding a status of property without deed of conv

Hi Sir / Mam I own a house in VIP road Kolkata. Around 10 years back (2006) I entered into an agreement to sell with a family at an agreed value. The buyer made a part payment for the property during entering into an agreement and were supposed to pay the remaining amount within 15 days. They asked me to give them the possession letter related to the property which I obliged to. They started living in the aforementioned property after the execution of the agreement. However they later on refused to pay the remaining sum while continuing to live there. In spite of repeated correspondence from my side to pay the remaining amount and complete the transfer they did not respond to any of our letters. I am still paying the municipal taxes for the past 10 years and there is no deed of conveyance that has been entered into. Please can you let me know the legal recourse available. Do I have the right to lawfully evict this person. Can he claim relief under specific performance of contracts. Will the suit be time barred in this case. Does the defaulting buyer ( without entering into a deed of conveyance) have any right to the title of the property