Is it permissible for a father to designate a portion of his property to one of his children in exchange for that child relinquishing his share of the remaining inheritance, and do the other heirs have the right to annul this agreement after the father's death, and if the agreement is permissible, does the son have the right to claim his legal share despite the documented commitment?

The agreement between the father and the son to waive the inheritance is void, because the son does not own the inheritance until after his father's death. Therefore, the inheritance must be re-divided according to Sharia. The structure built by the brother on the roof is his private property and is not part of the inheritance. If the warehouse is part of his share, then he has a greater right to it, and he has the right of pre-emption concerning it. The brothers must observe justice and affection.