What documenst are needed for promoting a land in Westbengal

We have an ancestral house built by my grandfather in Kolkata. It has three floors each of which he gave to three of his sons (my dad and 2 of my uncles). Mutation was done for all the three floors under my uncle's and my father's name after my grandfather's demise. Now, my father as well as my uncles are no more. Only surviving member of that generation is my aunt (wife of the youngest uncle) who is nearly 80 years old. She doesn't have any children. Given that the house is now nearly 70 years old and most of us (my brother and other cousins) do not stay there we would like to promote the property. My questions are: 1.What are the documents needed when we will be giving the property to a promoter? 2. Given that my youngest uncle do not have kids and in absence of any will, what happens to ownership of that floor? 3. In case through Hindu Succession Act we (myself and my cousins) do inherit that portion as well what are the documents we would need to have so that we can succesfully go ahead with promoting?