Partition deed cancellation possibility

Dear Sir/Ma'am My mother-in-law died in an accident in 2019. A year after this happened, my father-in-law told my wife that he would register the one & half-acre farmland as a Gift deed (it was promised during our marriage). Trusting her father, she signed the documents without reading them. Later realized that it was not a gift deed but a release/partition deed and it was written in it as 1 1/2 acre farm land for my wife and the remaining property ( land, house, sites) for him, almost a 20: 80 ratio. In 2021 my father-in-law got second marriage and now he is not interested to allow her daughter to visit his house also. My questions are 1. My father in law land and property was inherited from his parents and 1 acre of land and house were belongs to my wife's mother. He didn't have any assets in his name before this partition deed. But now he has an 80% share of the property. At this stage Is there any possibility to challenge the release/ partition deed to cancel? 2. Is there any possibility to stop further registrations on the above properties as he planning to sell or transfer to others? Please Advise. Thank you.