Holding Charges

I booked a 1 bhk flat in Bhiwadi, Rajasthan in 2013 at ₹19 lakh. Builder offered the possession in 2017 but I did not take the possession and did not get it Registered as I wanted to sell out the flat. However, when I actually tried to sell, market value of the flat was ₹10-12 lakh. I many times approached the builder for cancelation or buy back but he did not agree. Builder continued to accure holding charges, interest on holding charges, maintenance and Interest on maintenace. I approached the builder in April 2020 and did one time settlement of all dues but due to covid, could not take possession and didn't get it Registered. Now when I contacted the builder again for registery, he is again asking for holding charges, interest on holding charges, maintenance and Interest on maintenance from April20 to till date. Now my question is, is it ethical on the part of builder to ask for holding charges when the market value of the property is less than 50% of the original purchase price and when I have already done the settlement once last year in April? I am still trying to sell the property even at half the price as I need money now. If I find a buyer and sell the property, builder will ask for transfer charges, holding charges, interest on holding charges, maintenance charges and interest on holding charges. Do I have any option to get waiver from builder if I want to sell the property or go for registry? What are my options??