Force to pay Unjustified demand and delay in handing over the physical possession.

Dear Sir/sirs, I booked a flat in in April, 2012 in Ghaziabad (UP). The delivery period was 24 months i.e. up to 01.04.2014 but the builder has not handed over the physical possession till today. There was a condition in the agreement that builder will pay penalty in lieu of delay in construction maximum up to 5% value of flat. Accordingly, the builder has adjusted penalty amount i.e. maximum up to 5% value of flat in my due payment. Although, the flats were ready in June, 2016 but internal finishing work e.g. electrical, sewerage, flooring, white wash, sanitation, wooden work etc. etc. was pending till August, 2016 but despite that the builder issued the letter in August, 2016 and forced me to pay the balance dues whereas it was clearly mentioned in the agreement that balance 5% will be paid at the time of physical possession. Having, no alternative, I deposited my all dues including balance flat cost, stamp duty, advance maintenance for 2 years, electricity meter connection charges etc. in September, 2016 but for amount of Rs. 65,000/- approx. which was projected as interest in the possession offer letter, I requested the builder to provide me the details/breakup of interest but despite my repeated requests, the builder has not provided me the details/breakup of interest till today. Not only this, now the builder is asking verbally to pay holding charges i.e. maximum up to 5% value of the flat (Rs. 1,20,000/- approx.), without which he will not hand over the physical possession of flat. Are his demands valid under law and if the answer is "No" then please guide me to whom I should complain? Sir, I am very much upset and completely unable to understand what to do? I have paid my all hard earned money to the builder. With kind regards,