What is the ruling on wiping the white area behind the ears instead of wiping the head?
The obligation in ablution is to wipe some of the head; it is not a condition to wipe all of it. Wiping the white area behind the ears suffices for that. And Allah the almighty knows best.
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.
What is the ruling of Islamic Law regarding one who slaughters a ewe and it turns out to have been pregnant, and is it permissible to slaughter the ewe if one knows it is pregnant?
Praise be to Allah, and peace and blessings upon our master, the Messenger of Allah.
If a person slaughters a ewe and it turns out to have been pregnant, the fetus becomes lawful (ḥalāl) by virtue of its mother's slaughter (tabaʿan li-ummihā).
It is stated in Mughnī al-Muḥtāj (Vol.6/P.158): "A fetus found dead [after the mother's slaughter], or found alive but in a state resembling that of a slaughtered animal [i.e., dying shortly after], becomes lawful — whether or not it had grown fur — provided it is found in the womb of a mother that was lawfully slaughtered, whether her slaughter was by cutting the throat, or by an arrow or hunting dog sent after her. This is based on the ḥadīth: 'The slaughtering of the fetus is [effected by] the slaughtering of its mother' [narrated by al-Tirmidhī, who graded it ḥasan, and by Ibn Ḥibbān, who graded it ṣaḥīḥ] — meaning that the slaughter which rendered the mother lawful renders the fetus lawful as well, by virtue of following her; and because the fetus is one of her constituent parts, and her slaughter renders lawful all of her parts."
This ruling differs, however, from the case of one who knows from the outset that the ewe is pregnant [and intends to sacrifice her specifically as the udḥiyah while pregnant] — in which case, according to the Shāfi'ī school, she does not fulfill the requirement of a valid sacrifice.
It is stated in Ḥāshiyat al-Bujayrimī 'alā al-Khaṭīb (Vol.4/P.335): "A pregnant animal does not fulfill the requirement [of a valid sacrifice], and this is the authoritative position (al-mu'tamad), because pregnancy diminishes the quality of the meat. As for why such an animal is nevertheless counted as complete [i.e., fully valid] in matters of zakāh, that is because the intent there is reproduction (nasl), not the quality of the meat.". And Allah, the Most High, knows best.
What is the ruling on someone who possesses gold with the intention of saving/hoarding it, and owns nothing else — is he obligated to sell a portion of it in order to pay the zakāh due on it?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah ﷺ.
Zakāh becomes immediately obligatory on cash, and likewise on gold — that which is not designated for a woman's personal adornment— once both reach the niṣāb (minimum threshold liable for zakah) and a full ḥawl (lunar year) has passed over them. It is not permissible to delay payment when it is genuinely possible to pay — meaning, when the wealth and the eligible recipients are both available. It is stated in Mughnī al-Muḥtāj (Vol.2/p.129): "Zakāh is obligatory immediately once it becomes feasible to pay it, meaning when the wealth and the eligible recipients are both present."
The one paying zakāh must discharge the obligatory zakāh due on saved (hoarded) gold either from the gold itself, or from its equivalent monetary value, in the event that no other funds are available — since paying from the gold itself is the original default (al-aṣl). It becomes permissible to pay from other funds instead only because zakāh is built upon the principle of ease and leniency, as stated in Asnā al-Maṭālib (Vol.1/p.366): "When a full ḥawl has elapsed on wealth other than trade goods... zakāh attaches to the actual asset itself (al-‘ayn), and the poor effectively become partners in it — even, for example, [becoming partners] in camels through the value of a sheep [owed as zakāh on them]... Paying from other wealth is permitted only because zakāh is built upon the principle of ease and leniency."
Accordingly: the one paying zakāh must discharge it either from the actual saved gold itself, or by selling a portion of the gold equal to the amount of zakāh owed. He may also borrow money to pay the zakāh, or pay the zakāh in installments before the ḥawl is complete [as an advance payment]. And Allah, the Exalted, knows best.