Is it permissible, in Islamic law, for one of the partners in an undivided land to request their full share along the public road, along with compensation for an entrance to the remaining land, and are their abusive actions towards their siblings and neighbors permissible?

The actions mentioned in the question are morally reprehensible and evil deeds. They constitute oppression, transgression, severing ties of kinship, and bad neighborliness, which are darkness upon darkness. Their impact is severe in this world and the Hereafter if the perpetrator does not repent. The Messenger of Allah, peace and blessings be upon him, said: "There is no sin more deserving of Allah hastening the punishment for its perpetrator in this world, in addition to what He stores for him in the Hereafter, than transgression and the severing of kinship ties." Bad character corrupts good deeds, as in the story of the woman who prayed at night, fasted during the day, and gave charity, but harmed her neighbors with her tongue. The Messenger of Allah, peace and blessings be upon him, said about her: "There is no good in her; she is among the people of the Fire."