Project in NCLT, IRP Demand Default Payment via legal notice !!

I had invested in Lotus arena1 Sector 79 Noida in year 2014, Possession due date is over and construction is on hold since 2018.. we did not pay one demand raised by builder asking reason of stopped construction and requested cancellation.. builder refused to cancel and did not refund the money and replied to settle on possession ( Against the BBA cancellation clause which was to refund the money within 2-3 months grace period ). Possession due in Apr 2019. Now project is in NCLT and IRP is in the game, during COC buyers refused all resolution but participation is less than 66% hence IRP is still the game. Further, without any resolution plan, IRP send a notice to pay the due to the demand which we did not pay with 18% interest. Since no resolution in place and no hope in the future, we have to safe guard our interest and seeking a advice to reply to IRP or what best can be done in this scenario.