Registration of House under Paggdi System

I am staying in a building which belongs to registered public trust. We are not able to trace the trustees, probably they have expired. The person collecting rent is staying in the same building and he signs the rent receipt as the managing trustee and manager. We have no idea as to who has appointed him as a manager. He claims to be landlord. He is staying since 30 years. His father was the manager of the trust and he expired in 2008. In trust deed it has been mention that there is no manager. In BMC my house belongs to my grandfather. When the house was purchased by my grandfather there was no law of stamp duty or registration. We have preserved original rent receipt issued by the original owner who was the trustee. He has no legal hire. All the taxes related to government have been paid by the person collecting rent. questions 1)do i have to registered may house with any government authorities. 2.) Whether the person collecting the rent is landlord. 3.)if not whether he is a tenant.