Delay in Possession of flat along with price increase.

I purchased a flat of 916 sq ft (saleable) in Mumbai in November 2009 @ rate of Rs. 4000 / sq ft and possession date for the same was December 2012 (Carpet Area: 545) In December 2012 builder placed a meeting with all the members and said unfortunately he cannot give possession and he needs another 1 year. In July 2013 Builder requested all the members that everyone needs to pay premium charges of Rs. 1800 / sq ft extra because as per new government rule, fungible FSI has been incorporated hence this premium charges to be paid. Same meeting he mentioned building possession will be given in March 2015. Today August 2017 still no sign of possession and builder mentioned in RERA website that he will give possession in December 2022. Flat cost: Rs.36.64 Lakhs (as per original) --- AS PER MOU Flat cost: Rs. 53.13 Lakhs (revised cost after adding premium charges) --- ONLY VERBAL COMMUNICATION Amount paid till date: Rs. 21 Lakhs. (ALL RECEIPTS IN PLACE) My concern and require assistance on below: 1. If i want my paid money back, will i get the full amount. 2. Am i eligible to get compensation on paid money and what will be the maximum rate of Interest and how much time it will take. 3. If i plan to continue and take the possession in December 2022 can i get the flat at my original rate i.e Rs. 4000 / sq ft and what's the procedure to honor the original rates and how much time it will take, as builder is not ready to accept the old rates which he has mentioned in MOU.