Apartment Posession Delayed - Please suggest/help

Hello Lawyers, I had booked an apartment in Bangalore in February 2014 and as per agreement the builder was supposed to handover by February 2016. Currently, even the plasting work is not complete of my apartment. Additionally, there is no construction going on from the past couple of months. I have already released about 85% of my flat cost to the builder and paying almost $20k as interest every month. Some of us who have booked the apartment have gone to the builder and questioned him but he keeps promising us that it will be completed soon but has never committed on the date of possession. Now, we have decided that we approach a lawyer and file a case against him. Is it better if we do it individually or collectively? Which way proves to be stronger? Also, the agreement states that the builder is liable to pay rent after the stipulated period but when asked he tries to avoid. He is very unresponsive. I personally do not want to the apartment anymore and want to sell it to anyone who wants to buy as it is almost impossible for me to bear the EMI cost every month. Please help me find a solution to this and your suggestions would be valuable. Thank you!