Refund with interest aftr sale deed execution.

Sir, I booked a flat in Oct,2012 paying 7 lacs. Subsequently in January, 2013 i paid further which amounted to nearly 93%of the total value of the cost. The builder promised possession by December , 2014. But from 2015 onwards he started giving reasons n excuses and has not completed the project .From June, 2017 onwards he started pressuring to take the registration of the flat , unless which he wouldnot complete my flat. So taking loan , I executed the sale deed as i wanted to move into the flat. But I learnt in March 2018, that he has submitted in rera registration Dec, 2020 as the final date for completing the project . Also during monsoon this year , i was shocked to see sepage right thru the flats, common areas and basement. Second lift too is yet to be installed. He has applied for registration in rera , but it is not yet complete. Due to my failing health and the condition of the flat, project I dont intend to move in now. How can I cancel the deed and get the refund along with intrest and compensation for all the troubles i went thru ? Please help .