Sir since the builder has delayed and breached in agreement this amount to deficiency in service so for that you can issue a legal notice to builder asking to refund complete amount with the interest as he has breached the agreement and further there shall be delay as project is not likely to complete before 2020.
Further the RERA and demonetisation cannot be held reason of delay as held by national and state consumer forum in many order.
If on the legal notice the builder does not refund the amount with interest file a Consumer complaint before the appropriate jurisdiction demanding refund along with interest compensation and the litigation fee.