Is it permissible for one who sacrifices on behalf of another, with the latter's permission, to eat from the sacrifice?
It is permissible for someone who sacrificed on behalf of another with their permission to eat from it with their permission, and they stand in their place (act as their representative) in distributing it.
It is stated in Nihayat al-Muhtaj ila Sharh al-Minhaj (Vol.8/P.141): "And he—meaning the one sacrificing on his own behalf, provided he has not apostatized—has the right to eat from a voluntary sacrifice and his sacrificial gift; rather, it is recommended. As for an obligatory sacrifice, it is forbidden for him to eat from it, whether it was designated as such initially or as a liability in his dhimmah. And excluded by what has preceded is if he sacrifices on behalf of another, or if he apostatized, then it is not permissible for him to eat from it, just as it is absolutely impermissible to feed a disbeliever from it."(The text I found indicates the impermissibility of eating) ???
And it is stated in Hashiyat al-Jamal ‘ala Sharh al-Manhaj (Vol.5/P.262): "If a person offers a sacrifice on behalf of a living person with their permission, does he act as their representative in distributing it—on the grounds that permission to sacrifice is permission to distribute it—or does it depend on their explicit permission? This requires consideration, but the first view is not far-fetched." And Allah the Almighty knows best.
Does touching women temporarily forbidden in marriage nullify ablution?
It is prohibited to touch, or to shake hands with such women as they are considered strangers, and doing so nullifies ablution.
Who is the one required to slaughter the 'aqīqah?
All praise is due to Allah, and may peace and blessings be upon our Master, the Messenger of Allah.
It is Sunnah for the 'aqīqah to be slaughtered by the guardian of the newborn — the one upon whom the child's financial maintenance is obligatory — provided he is financially capable of doing so. 'Alī ibn Abī Ṭālib, may Allah be pleased with him, reported: "The Messenger of Allah ﷺ performed the 'aqīqah for al-Ḥasan with one sheep." — Narrated by al-Tirmidhī. And Allah Almighty knows best.
What is the ruling of Islamic Law on a father shaking hands with his son’s wife after she has been divorced three times?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah.
The wife of one’s son is among the women permanently prohibited to the husband’s father as soon as the marriage contract is concluded, based on the saying of Allah the Exalted: “Prohibited to you are your mothers, your daughters, your sisters, your paternal aunts, your maternal aunts, your brother’s daughters, your sister’s daughters, your foster mothers, your foster sisters, your wives’ mothers, and your stepdaughters under your guardianship [born] of your wives with whom you have consummated marriage. But if you have not consummated marriage with them, there is no sin upon you. [Also prohibited are] the wives of your sons who are from your loins, and that you take [in marriage] two sisters simultaneously, except for what has already occurred. Indeed, Allah is ever Forgiving and Merciful.” [al-Nisāʾ/23]
This prohibition begins once the son’s marriage contract with his wife is complete, and it remains in force even if the son separates from her before consummation or before any seclusion (khalwah) with her. It is therefore permissible for the father to shake her hand and to be alone with her, provided there is no fitnah (temptation) and no suspicion.
It is stated in ʿUmdat al-Sālik (p. 204): “It is forbidden to marry… the wives of one’s fathers and of one’s sons. All of these women become prohibited by the mere contract, … all of that being a permanent prohibition.” End quote, with slight adaptation. And Allah Almighty knows best.