Ancestral property of my mother

My mother had property that she inherited. After she passed away in 2010 in her will she stated that the said inherited property be given to her brother. Me and my 4 siblings who were the legal heirs signed a no- objection letter to transfer the property in my uncles name in 2011. However, my uncle has not yet transferred the property to his name. Now the issue is that back in 2011 when we signed the no objection letter we had no interest in the land as it was in our native place. Now, however my uncle wishes to sell the land. We are not in favor of this as it was her wish that her brother uses the land to build his residence. My uncle also owns the adjacent plot of land that he acquired through inheritance. My question here is 1. Is the NOC letter still valid or has it's validity expired 2. If expired, can we refuse to give him a new NOC letter 3. If the NOC is still valid can we object or put a stop on the transfer of property 4. As she has stated in the will that the property be transferred to her brother and if the NOC is no longer valid can we claim our rights to this property