how to file a recovery suit against the builder

Hi , My bro in law expired in Dec 2014. He had bought a unitech property - a 3 bhk in crest view , Sec 70 under a subvention scheme from Icici bank under joint name with my sister ( house wife ) in 2013. Construction hasn't started as yet. They had paid 20 lacs cash down and 75 lacs through bank loan . The agreement mentioned 12% annual interest in case property wasn't handed over in 3 years. We need money back as 80210 is the EMI which my sister obviously can't pay. I have been paying it for the last 26 months with the hope that work will start. What's the legal advice to get the money back and also to get the emi stopped immediately ? With two small daughters ( 12, 9 years old ) my sister has joined a school as a teacher at 30k salary per month. On compassionate grounds how soon can justice be expected and how ?