Property payment last instalment

Dear Sir Namaste. We bought an apartment at Pashmina Waterfront , Budgiere ,Bangalore in 2012 and they said they will handover the property by Dec 2015. Now the property is delayed for 4 years. We availed homeloan from SBI. Bank refused to release the last instalment of about 3 lacs and from our side there is an amount of Rs 12lacs due from side amounting to about Rs 15 lacs over all due to the builder. We couldn't pay 12 lacs as both me and husband didn't have jobs and financially we were more burdened. Now as per the agreement , builder is refusing to pay the penalty amount of about 8lacs due to us for 4 years stating penalty can be paid to buyers who have paid all the amount . Now we are not in a position to avail top up loan also as property is not registered. SBI will give top-up only on registered property. We do not have enough money to pay 15 lacs + registration 5 lacs. We have paid about 70lacs out of 83lacs promptly. Please let us know sir if there is any way we can convince /fight with the builder . Thanks and Regards Vaijayanthi