Demand adjustment with compensation/penalty amount...

I am from Delhi-NCR and have booked a builder flat in 2010 in my region for which possession date was on 2012 as per agreement but still not have its possession in my hand. Now just because of this i had given extra enhanced EDC charges which was raised by the government in 2013-2014 and now also received demand of VAT charges which i need to pay extra as it is come in law now. Now due to delay in project i have to bear all these extra costs. 1. I have to bear this extra cost or builder need to pay it from his earning/revenue?? 2. As per BBA, in case of any delay in demanded payment, builder has right to take 18% interest which is also on compound value quarterly. And in case of delay in possession from builder they have only 5% penalty clause on BBA. Is it legal? Can we fight for this. means i also want 18% penalty from builder side as it is already 4 years delay in possession? 3. Can we have right to adjust the VAT demand and other demand from builder with the penalty amount which they need to pay as per BBA means 5%. 4. For VAT they are saying that in case of delay in VAT payment, they will charge 3% interest per month. But as per BBA, we are only liable on for 18% per anum. Is it legal or not? Please advice me on this.