Does khasra matters if purchase is done by municipal numbers

We purchased the property with chain of documents in 1990 through registered power of attorney, we started renovation in the said premises in 2011, through fabrication we were traped by dealer and land mafia and they stared asking for money . we denied for same then after they filled the suit against us by making MCD a party to stop illegal construction and said he is the owner of the property as per khasra demarcation report. i went to Tehsil dar office to confirm there i got the same demarcation in record showing that khasra belongs to him. i m confused that we bought the property in 1990 through municipal number and now he is claiming the ownership through demarcation? my first question is that possible to do demarcation in the area which is urbanized . 2. All sale purchases was done by Municipal number in that case khasra matters?.3.He has only the demarcation which is matching with records of tehsil dar , and we have all the documnents since 1960 showing that premise belongs to u