Cheating / Fraud by Builder - Builder has performed sale deed (2020) after my agreement for sale (20

Hi All, I have purchased the flat in 2014 and we have done sale of agreement. I have also taken the loan from HDFC Bank which i am paying the EMI. This project was delayed by builder for 5 years, since 2018 he is asking for extra money, and I denied hence he has not given possession to me in 2021. Now i come to know that he sold the same property in 2020 to another buyer. I am looking for couple of option which i have started but need your advice-- 1. We are filing a FIR with police - In process 2. Question 1 - Should i go to consumer court or go to RERA ? Which one is best for my case. 5. How can i file a case to existing person who is staying in the same flat, I have my agreement for sale in 2014, I have bank loan and currently paying EMI for same flat. Is there any solution to get back same flat and other person should also fight the case. He has not done his due diligence to check NOC of the flat. All these happen because i move from the city and settle other place for my job. It's my hard earned money. Please advice where will i get fast solution.. Thanks a lot in advance.