I am a LANDLORD What rights i have on the property ?

I have a property in mumbai which is around 2400 sqft given on pagdi to 10 tenants. Its been 30-40 yrs that they have been staying there,when my grandfather had built the chawls. After my grandfathers death my father did not look out for this property as he was busy making his life and jumping hurdles after the death of my grandfather. The lease rent was very low and they refused to pay and kept on saying next month next month. Its been 20-25 yrs that they have not given the rent. 2-3 out of 10 have sold their chawls which were given on pagdi by my grandfather. 1) what legal options i have for this property ? 2) will the property called as slum ? 3) can i develop and take the fsi as slum? 4) should i remove them or give them the same size if i construct? 5) if they are ready to move is it necessary to give them the rent so they can relocate? 6) if it is necessary to give them rent should it be according to the current rent which is very very low ? 7) what about the people who have no consent of ours when they bought the chawl from old tenants ?and what if old tenants who sold cant be find?