• Transfer of title of ownership in exchange contract

My ancestors came from hariyana to settle in delhi in 1910s. My great grandfather purchased a piece of land, which was divided among his four kids during his lifetime. but before separate construction work for building houses was carried out, the land was exchanged with some other people of our village in return for their land. Unfortunately, no documentation work was done by my ancestors. It was not only our family, but some more families also did the same, nome of who made any documentation for the exchange.
A few days ago when one of the families tried to sell their part of land (which he had got in exchange) they found that the land so exchanged, was still registered in the name of the other party of exchange. When the family proceeded to complete the documentation so as to complte the sale and thus, they went to that person requesting transfer of ownership and power of attorney and other relevnt documents needed, the person refused to transfer the title saying that the land had been exchanged for the purpose of residing and could not be sold. This implied that like them, we too do not have any right on our property.

I wish to seek legal advice in this respect on the dollowing matters:
1. How can i obtain legal title of ownrship?
2. Is it legally correct on their part to restrict us from selling the land?
3. In case we do not wish to reside in the exchanged property, will the exchange hold any further relevance? And will we have ownership of our land which we had originally purchased?
4. Whom should i proceed to and how should i initiate?