Delayed penalty payment from Builder on Resale Flats.

Dear Sir, I have purchased a flat in January 2018 from a seller who was the first allottee (he had purchased it in May 2010) At the time of Purchase the flat was under construction. The allottment was transferred to me by the builder and transfer fee was charged. My name was endorsed on the original BBA. The possession of the said flat is now offered on 14 Feb 2019.The delayed payment penalty starts after 42 months @Rs. 5 per sqfeet for first year and thereafter @ 15 Rs per sq feet for any subsequent delays (Total Delay is 62 Months) That means that delayed payment penalty starts from 1 Dec 2013 as per BBA. Th. But now the builder says that in case of resale, no such penalty is paid to the second allottee. However the BBA does not have such a clause. The catch is that the one of the affidavits that I had signed and given to the builder for transfer of flat had a clause that I will not claim for any delayed possession penalty payment. Sadly, I had ignored this while signing the papers and only got to know it recently. Can I still challenge this in courts? Can I still get the penalty amount at the time of possession? What legal remedies do i have?Also the builder has increased the super area by 7% and demanding money for the same at the possession.