Procedure to exit property allotment

Before RERA was anywhere in discussions, I had booked a flat with a lesser known Builder in Ulwae. I paid 8 lakh and got an allotment letter with a 3 year PDC equivalent to 8 lakh+10% simple interest which was to be used in case project does not take off in 3 years and I wish to withdraw. Now after completing 3 years, Builder has not even got the building plan approved, let alone preparing land for construction. As a pre condition to exit, Builder wants us to surrender the allotment letter and old cheque for another cheque. I am skeptic of his intentions as for all practical purposes if I don't hold an allotment letter, and his cheque bounces, I would not have any means to prove this cheque was legitimately issued to me to exit the unregistered deal. We did a NEFT to the account from which the original cheque was issued and as expected it failed. Is the account is not active anymore, hence Builder is issuing us another cheque. Please advise if we handover the only proof of having paid him our money, do we still legally hold a chance to contest him ??