it is illegal extortion by the original allottee at this stage. Why dont you approach the vendor who sold you the property and hold him liable to get the mutation on your name from original allottee.
The original allottee is taking advantage f your need and helplessness hence try for an amicable settlement and get his objection withdrawn from GDAt enable you to mutate the property on your name. If this process is not favoring you, then you may resort to due process of law by first issuing a notice to the vendor who sold you the property instructing him to cooperate to mutate the property on your name failing which he will be held responsible for the legal consequences. This will certainly invoke some response.