Partition of undivided hindu familiy

as per the Govt records 2.5 acres (ancestral) in my name, 1.5 acres (purchased by my father) in my brother name and 3.5 acres (ancestral) in my father name. we divided our property and written on stamp paper of Rs 20/-. in 2014 as per the agreement I got 3 acres and my brother got 4.5 acres and my father did not get anything. and all other movable assets are with my brother. iam serving govt employee., iam not satisfied with the above agreement. 1.can I cancel above agreement (my father and brother accepting above agreement). 2. if I approach court, how much share I will get. 3. my brother is enjoying entire property iam not getting any income as share from property. 4. if my brother purchase any other asset, can I get as share from it.