Builder of an Apartment trying to sell the flat which was sold to me

In January 2009 , i bought flat with builder & the apartment is in semi finished stage and due to complete by Sept. 2009. I have entered into an agreement with him against the payment of Rs.1 Lakhs. Subsequently i paid Rs.7 lakhs (some through cheques & some in cash for which i have the recipts). As per the agreement i have to pay him Rs.27 lakhs (incl. amenities) & he will register the flat after payment of full consideration. One clause in the agreemen also syas that ' the builder has to give the possession at or immediately after the registration. Please note that no specific time frame was mentioned in the agreement. In May 01st week i applied for bank loan and i gor the sanction also and i have the balance money also arranged (For wsi have proofs). The builder fully cooperated and even showed original documents on 19.05.09 to the bank's lawer for legal openion. I deposited some money with the bank as margin money also. All this bank wok was happened between 10.05.09 to 02.06.09. Now builder is threatening me to pay all the money immediately and get the registration. I offered him 80% since it is not yet finished.

a) can i aproach the court for orders to Registar not to register in anyone's favour

b) can the