Capital gain from ancestral property

We got a share from our ancestral property in 2010, after my father passed away. The total amount received was Rs. 30 lakhs. I, my mother and brother were legal heirs to the property, so we were given an equal share of 10 lakhs each in the form of cheques. We deposited this in three separate capital gain bank accounts of my mother, brother and mine. Within two months of sale of ancestral property, the money was used to purchase a joint residential property worth Rs. 31 Lakhs by all three of us. It was an under construction project and the flat was to be delivered till March 2013 (as per what the dealer had committed). During these 3 years we paid all the installments to the builder per the schedule. The last installment was due to be paid at the time of possession. The project got delayed by 4 years and the builder is offering possession of the flat now. The bank is refusing to release the final installment without the tax return. My questions are: 1. Please explain the tax liability in this case. We didn’t file a tax return for the capital gain from ancestral property as we reinvested the amount to buy a new property within 2 months of selling the ancestral property. Also, the new property was of an amount higher than the money we received from our ancestral property. 2. The project completion got delayed from the builder’s end. So were we suppose to file a tax return in these 4 years of delay? 3. Please explain how can we pay the last installment to the builder from our capital gain bank accounts?