Is it possible to challenge the Relinquishment deed or Hakka sod Patra

Is it possible to challenge the release deed? It was signed by my father under pressure of their brother. After the death of my grandfather because of the incomplete construction my dad's mother wanted to complete the house, and my first uncle was trying to take the responsibility financially as it was Ekatra Kutumb Paddhat. A. But my second uncle influenced everyone to take a loan for the remaining house. In this case to get a loan (only for the remaining work which is RCC Slab) from LIC he wanted to show the property on his name, because he was going to take the loan on his wife's name who had a gov job at the time. So he asked everyone to sign on the Relinquishment deed or Hakka sod patra. And he has mentioned a return amount of 30000 in the document. The document was signed by 1. My first uncle 2. My second uncle 3. My father 4. My grandmother The witnesses who signed the document are not clear there is only one witness and the same names english signature is written as a second witness. B. In return my father wanted a document signed by everyone mentioning this business is done only for the construction purpose after that the division should be done ethically. In that he clearly mentioned the 30000 rs mentioned in the above document is wrong and it is written only for the loan purpose. The document is written on 10rs stamp paper. The original document is with my first uncle's daughter. And it is not registered. Is it still valid? C. We are living in one room of the bunglow which has 6 rooms in total. Other 5 rooms and bunglow is being used by my second uncle from thirty years and we are also living there from 30 years ( in the case of adverse possession) there is a workshop which is older than the bunglow and it is built by my dad entirely and there is light connection from that day till today. Which proves possession older than his connection. This is the case of fraud but is it possible to challenge the deed.