Redevelopment Issue By Builder.

Dear Sir, I am Ashim Das from Mumbai city. I have some confusion about my property. I think I am being misguided by builder and also my lawyer. So I am writing you my issue. Please guide me. In 2010, my parents had given the permission to our builder to redevelopment our society where we have our flat by writing agreement and builder has taken all the permission from BMC to redevelopment, BMC has given the permission to builder to redevelopment the building within the year of 2021. But after that there is no any agreement made any property allocation agreement which clearly mention that how much sq ft flat we will get instead of our present property. In 2012, my parents are died and the ownership of flat transferred in my name as inherited. But the builder could not start his redevelopment work due to his problems. Now the builder wants to start his work. But his proposal is not favorable to me because he does not want to give adequate sq ft flat which I need. Even he does not want to give me present sq ft flat in which I am living now. I have listened that as per BMC act if any builder can not occupy the 70% property allocation agreement of the builder then he can make start his project. The builder is unable to occupy the 70% signature to his projects. If I sign then his 70% is complete. If the proposal is favorable to me then I will sign agreement. But the builder does not agree and he threaten me that if I can not complete the project within the year of 2021 then he will sue on me for his loss. Now my question is that the agreement which signature by my parents who are no more, to builder for permission to his project, can be implemented on me ?