Late possession of flat

I had booked a flat in an under construction building in March 2013. The possession date mentioned in the agreement was Dec 2013. The construction is not get completed. But I have paid 99% of the amount as per the builder demand letter.The work progress has been very slow. The builder keels giving expected date for possession but has not delivered on his promise. He is giving reasons like delay in getting approvals from municipality. Also he wants permission for 2 additional floors. He is saying that building additional floors wont affect the possession of the 13 floors (as per original plan). He is saying that he will provide temporary sintex tank instead of building overhead water tank. Also lift will be installed. Can the municipal authorities provide such a part OC? I am paying rent and hefty EMI. The builder is not ready to pay compensation as there is no such clause in the agreement. The work is not halted but the pace is slow and it looks it will take almost a year to complete. What are the legal options available?