What all are the rights of legal heirs ?

My dad has 4 brothers. We live in a DDA Janta flat in Delhi which was bought in the name of my grandmother who gave it to 1 of my paternal uncle in her will. The house is still unregistered, the electricity bill etc still comes in the name of the person from whom the house was bought. Two of us families live here. We live on first floor, the other one on second floor is my another paternal uncle's family(not the one in whose name property was transferred). The address for both the floors is exactly the same. Now, I have a few queries :- • As legal heirs of the property, what all rights do we have ? Can the person with the will in his name sell the property without any NOC from us ? Can he register the house to his name without any NOC from us ? • Will it be possible to sell only our house on 1st floor, without selling the one on 2nd floor. I am asking this because the family on 2nd floor are not willing to sell the house. So, in this case, what all legal rights/choices do we have ?