1. Intimation of cancellation of booking should be sent through a lawyer's notice, not an email. Be that as it may, you will be free to sue the builder in the consumer forum for refund of the money with interest if he does not refund on his own accord.
2. If the builder did not pay interest to the bank then it is for the bank to initiate recovery proceedings against him in the civil court. It does not curtail your right to recover your money from the builder.
3. The date of delivery of possession mentioned in the agreement is sacrosanct, failing which the builder has to deliver the possession in a reasonable time.