Unregistered mortgage deed of 2000 and unregistered sale deed of 2002

The seller in Maharashtra (now deceased) owned 1 hectare and 61 R of agricultural land. He divided entire land between his three sons during his lifetime. The land of 40 R belonging to his elder son was mortgaged on 27.6.2000 on stamp value of rupees fifty for consideration of Rs.17000/- by deceased father and elder son. On failure to pay mortgage amount, he made sale deed dated 11.5.2002 on stamp value of rupees fitty for consideration of Rs.55000/- by father son duo. This land was tenanted land and cannot be sold without permission of Collector. Now this condition has been removed u/s 43 of Maharashtra Tenancy Act 1948 (for holding land for ten years or more). The seller died in 2009. On his death the names of his three sons were recorded in mutation records. Both the unregistered mortgage deed and sale deed has thump impression of the seller and his elder son. The elder son started obstructing my peaceful possession on 15 years. I filed RCS for injunction. Exhibit-5 order was in my favour. The elder son filed Appeal . The District Judge set aside Exhibit-5 order. I went to High Court and obtained stay order. The elder son has raised a loan of Rs. 2.50 lakhs in 2019 on sold property. What are my defences in the WP pending before the Hon'ble High Court?