Is it permissible for the grandfather to sell his house to his daughters, then for it to be sold again by another person (who bought it) to the daughters and registered in court, in order to disinherit his disobedient son and his other daughter, and to protect his divorced daughter and her children from homelessness after his death, knowing that he owns nothing but this house and his pension?

There is no doubt about the prohibition and ugliness of disobeying one's parents. It is even more reprehensible when an elderly parent is beaten. The recompense is of the same kind as the deed, so they must repent immediately. As for the grandfather selling the house, if it was a real sale with all conditions fulfilled, then the house belongs to the buyer, and the heirs have no right to it. If it was a nominal sale, then it is considered a gift. One should then consider whether the gift was completed during the grandfather's health and whether possession was taken; if so, it is enforceable. However, if it was completed during his death illness, it takes the ruling of a will, and the house belongs to all heirs. This matter requires direct consultation with specialized scholars, and in case of dispute, the matter should be referred to the Sharia court.