Builder not giving possession and demanding more money

I am an NRI and have brought a flat in Andhra pradesh. Builder completed the flat (with almost 2 years delay) but not giving the possession and demanding more money (10 Lakhs more) by charging Interest saying that there is a delay in bank releasing the installment. But i checked with the bank and got in written from bank that they released based on the technical evaluation of the construction. But builder is not agreeing to that. He is not even ready to give the reasons for extra charges in written. My parents are aged and cannot fight with the builder. Here are my questions. 1. Can i go for a police case on the builder for not giving the possession? Builder is demanding more money and threatening my parents. 2. As per the registration, Builder promised to complete in 2 years with 3 months grace period. If i have to go for consumer court, does the 2 year period time limit starts from the 2 years or 2.3 years. I mean the limitation of the case has to be filed in consumer court will start after the grace period or before the grace period of 3 months. i am at the edge of the completing 2 years, appreciate your quick response. Thanks KK