Builder has charged an interest due to delay in Agreement and first Disbursement.

My new flat was allotted at 22nd Feb 2020 (construction was at base stage), my Agreement was delayed due to COVID and was done on 26th May 2020, First Disbursement through bank happened on 2nd June 2020 (39% agreement value). My own contribution was set to 70% and 75% (5% each) of the building completion (mail confirmation). Till this everything was fine. So the demand which followed should have been of 15% of Agreement value, but they sent me the demand to clear the GST amount of 177600 Rs. (14th August 2020). While mutual agreement and via email, I was bound to pay the GST as per the bank disbursement from time to time. But a sudden ask for paying this GST started the issue as I did not have the money. I asked the bank to pay the amount but the bank denied me to pay it and said that we will pay the GST in parts with every demand the builder asks (I have a mail confirmation from Bank). I conveyed the same to the sales team and they agreed. Till the time actual demand was sent of 15% (11th Sept 2020) and they had charged me the interest as the First demand which was the GST was not payed in the stipulated time (30000 Rs. Interest). Further all upcoming demands were cleared leaving the Interest behind. Now after completing the whole payment as per agreement value, the builder is not waving off the Interest and delaying my Possession since 2nd April 2022. Other Flats in my Building are already been given possession to the owners. Now when I'm asking for the waiver they and conveying me that there is a delay in your agreement and First disbursement which should be done in 30 days from Allotment so you have to pay the interest. In the allotment letter I do not see any pointer that if the agreement is not done in a specific time then I have to pay the Interest. Question: 1. Am I liable to pay any Interest for a delayed payment before the Agreement registration? 2. What are my option if the builder still doesn't agree?