Legality of cancellation of agreement for sale

I have entered into an registered agreement for sale in the year 2006 but the purchaser failed to pay the amount in the stipulated time and cancellation clause is also in that agreement .then i re-registered the said agreement in another person name but the possession is in hand of the old purchaser meanwhile the first purchaser took out the duplicate agreement copy from the registration office and on that behalf electricity meter adhar card etc and approached the society registrar to compel the society to induct his name in the society but there he failed as he was not having possession letter. thereafter in 2016 he approached police station that he is been frauded by the builder and on his application the police is harrassing me Now i want to know the following : 1. whether his application stands where he has agreed that he has not paid the entire amount 2. the amount is not received by me of the second owner nut it is been received by the land owner as the flat belonged to the land owner and the first owner amount was also taken by the land owner as the flat belonged to the share of the land owner.then who is liable, i or the land owner 3. the police is telling me to give the original paper ,should i give or what to do please suggest