Regarding delayed possession compensation as Rera act

I have booked the flat in pune dated 2019 first quarter, I did sale deed where possession date was mentioned as June 2020. However I have not received possession on June 2020 but builder got relief by Rera as per Covid Pandemic for 6 months extension i.e July to December 2020 . As per this guidelines from Rera, builder missed Dec 2020 possession date as well for which 6 months extension was given. So as per Rera section 18 and 19, builder is liable to pay compensation as Interest on total amount paid by Allottee till now. Builder announced ₹15000 from January 2021 till time of possession/ Completion Certificate received. But I have told builder that ₹15000 amount not accepted by me as builder should provide compensation as per standard interest rates for the total amount paid by me till now I.e aa per Rera rule which is coming around ₹50000 onwards monthly. My question is, if builder denies me to provide compensation as let Rera act 18 then where should I do the complaint? In Rera as well as consumer Court as well tribunal court? Which complaint will provide me faster resolution on co compensation? Also what is current current interest rate as of April 2021 for which builder need to pay interest to us on total amount paid?