Land owner denying handover - asking for past maintenance which was never communicated or agreed

I have booked a flat from landowner on 5th August for 59L, paid him all his dues and registered flat in my name on 5th Oct in Bangalore. As a process, he needs to handover the flat. Now, in my last meeting, he is asking for additional 36,000 (12 months x 3000/month maintenance). I agreed to pay, but said will pay from date of handover to 1 year. Now, he has made a story saying this is investors flat and that maintenance is due for 1 year. So, you need to pay from Dec., 2018- Nov., 2019. Trust me, this has never been in discussion, either in writing or orally. I have all papers handy where maintenance was never agreed. Am okay to pay for 1 year advance but why of past when flat was never owned by me. In fact, I have proof where he states total cost is 59L and done. The delay in handover is letting me pay EMI, but not to start my interiors. I know this is illegitimate demand and wish to sue him. I have sent him a mail stating handover my flat or face legal consequences. He is threatening of reselling the flat otherwise. Please help. Happy to connect.