Noc from Builder

I hold a flat in a building after Redevelopment. The flat has been registered in my name since Two and half year. OCCUPATION CERTIFICATE yet to come Society is not formed. Builder gave us possession for fit out on 15/08/2019 with an fit out agreement and also allowed us to stay stating in the agreement that it is on our (tenants) request he is allowing us to occupy the flat. The property is still in builders name till date. He sends me a maintenance bill on a plain piece of paper including property tax on November 2021 for payment. Am I liable to pay the above mentioned charges including property tax. I would like to sale my flat as I cannot wait for OC TO come and formation of society. Buyer wants title clear and no dues certificate from Builder,that is NOC from builder. Am I suppose to pay maintainance including property tax to the builder even if there is no OC. Is it necessary to take NOC from Builder even if the property is registered in my name,and sell the flat directly to the buyer. Will there be any legal implications on me or a buyer post sale,registration in buyers name by the builder.