Purchase Flat Under Subvention Scheme

What should I do now? I have purchased a flat in Noida extension under subvention scheme in project SAHA MEGHDUTAM ENCORE. For that subvention scheme, I paid the builder 500 rs per square feet extra as compared to CLP (Construction Linked Plan). Builder committed me subvention till possession and gave assurance in writing over his letter head for this but didn’t include this clause as part of BBA (Builder Buyer agreement). Although that time their tie up with bank for subvention was only for an year so as per promise till possession, he also gave me confidence over mail as well, to extend the subvention period with bank. In the Current situation builder has defaulted. The Matter is in NCLT and IRP appointed asked me for any agreement for extended subvention to accept pre emi as part of claim acceptance. I don't have any such agreement except the letter head issued by builder along with mail conversation. . Am I not entitled to claim pre emi paid.