Builder is Delaying to furnish the NOC to Register

We have booked a flat in the City of Mangalore and have paid 70% of the value of the property in stage payments during the course of construction. The property is now ready for possession (though the common areas are yet to be finished) and the 30% is due to be paid during the process of getting the registration. The 30% was delayed to be paid as the construction was delayed beyond proportion. We have not obtained any loan for buying the property. While inquiring, the builder denied that there was any loan financed for the property, we came to understand that the full property has been mortgaged by the builder with a nationalized bank. On our insistence to obtain NOC to register from the nationalized bank, the builder obliged to provide the same though he objected initially. Now it has been almost 2 1/2 months since the NOC to register has been applied jointly by us and the builder with the bank, the builder is dodging us with frivolous reasons and insisting on getting the registration done without the NOC to register. We on our part are adamant that we will not do the registration without the NOC to register from the bank. However some of the buyers, unaware of the fact of the mortgage matter have done the registration. In some cases where there are loans obtained by the buyers, the bank has given the NOC to register. While we approcached directly to the bank to provide us with NOC to register, the bank communicated to us stating that the NOC cannot be provided and the bank is initiating recovery procedures. Please advise the recourse available to us. Can the bank deny us NOC to register while it is issued to the some of the buyers? What recourse do we have against the builder? Can we ask for refund of our payment with interest?