Late possession

Hi My builder promised the possession in Mar'24, but it was delayed & a mail for possession received in Sep'24. Which is already delayed. In the mail, they asked for late payment interest charges. Which I paid & asked them for the further process. They told me that first registry will happen & then possession will be provided. And it will take 2-3 months. Later in Dec'24 they asked me to pay IFUD/operational charges before going ahead. I cleared those also. Now they are delaying the registry saying there are number of files in the queue, and you will be notified once your file is processed. My questions are: 1. Is it OK for the builder to charge IFUD charges before the possession is not completed? As when i raised this question, they only say that they are charging it from Feb'24 from everyone. 2. As per them, according to rules, the project can be delayed by 6 months & they have sent mail for possession in Sep'24 which is exactly 6 months from expected possession date. Can I file a case for the interest for the delayed possession? As for me the possession is delayed more than 6 months. by sending a mail doesn't confirm that possession is given. Also, only the flats are ready but the premises are still under construction like boundaries are still not completed. Please suggest.