Flat Sell - Builder is charging for NOC

I purchased a flat in Virar,Thane, Maharashtra 10 years before in under constructionphase, now,Recently I got possession, society is not formed yet, but due to some financial problem i want to sell the flat on immediate basis, but builder is asking additional money for giving NOC (transfer charges), also he told me when you booked the flat that time RERA was not there, but from 2017 RERA come into picture, so you have to pay some difference amount as RERA charges, initially flat size was 555 but during your new sale agreement your flat size will become 615, it is really confusing for me, as there is no written agreement / communication happened between me and builder about this additional charges, and when i want to sell the flat that time he is asking about this additional money, on top of it he is charging 500 rs/Sqft changes as infrastructure development changes, My sellable price is 28L, so there is no benefit to me if I sell this flat with such condition.