Can a woman perform I‘tikaf in her home?
No, a woman's I‘tikaf is not valid if performed at home, because her home is not a mosque.
What is the ruling on men wearing rings (those made of silver and of other metals, such as iron), and are there conditions for men wearing rings?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah.
It is sunnah for men to wear a silver ring on the right hand, following the practice of the Prophet (peace and blessings be upon him). It is reported in Ṣaḥīḥ al-Bukhārī, on the authority of Anas ibn Mālik (may Allah be pleased with him), that the Messenger of Allah (peace and blessings be upon him) took a silver ring and had “Muḥammad Rasūl Allāh” engraved on it. He said: “I have taken a ring of silver and had ‘Muḥammad Rasūl Allāh’ engraved on it, so let no one engrave the like of its engraving.”
It is a condition that the silver ring not exceed the size customary in the local norm (ʿurf). If it does, that is extravagance (isrāf). A ring made of a metal other than silver, such as iron or copper, is permissible to wear without disapproval (karāhah), except gold, which is forbidden (ḥarām) for a man to wear.
It is stated in Mughnī al-Muḥtāj (Vol.1/p.586): “It is permissible, without disapproval, to wear a ring of iron or lead. It is sunnah for a man to wear a silver ring on the little finger of his right or left hand. Wearing it on the right is better, and it is permissible on the left, and on both together.”
It is also stated in Mughnī al-Muḥtāj (Vol.2/p.97): “It is lawful for him, that is, the man, and likewise the khunthā (person of indeterminate sex), indeed all the more so, to wear a ring of silver, by consensus (ijmāʿ), because the Prophet (peace and blessings be upon him) took a ring of silver, narrated by the two Shaykhs (al-Bukhārī and Muslim). Wearing it is in fact sunnah, whether on the right or the left, though the right is better according to the sound position, as stated in the chapter on clothing in al-Rawḍah… The Shāfiʿī jurists did not specify the permitted size of the ring, and they probably relied on custom (ʿurf), that is, the custom of that country and the habit of people of his standing in it. Whatever exceeds that is extravagance, as they said regarding a woman’s anklet. This is the reliable position (al-muʿtamad).” And Allah Almighty knows best.
What is the ruling on a mother giving the Zakat of her wealth to her children?
Praise be to Allah, and peace and blessings be upon our Master, the Messenger of Allah.
It is permissible for a mother to give her children from the Zakat if they are among those who are eligible for it—such as being poor (Fuqara), possessing no wealth, and not being sufficiently provided for by the maintenance (Nafaqah) of others. This is based on the statement of the Messenger of Allah ﷺ regarding Zaynab, the wife of 'Abdullah ibn Mas'ud (may Allah be pleased with them both): (Your husband and your children are the most deserving of those upon whom you spend in charity) [Narrated by Al-Bukhari].
It is stated in [Al-Hawi al-Kabir, Vol. 8/P.537]: 'As for the wife, it is permissible for her to pay her Zakat to her husband from all the designated shares... Our evidence is the generality of the saying of Allah the Almighty: "Zakat expenditures are only for the poor and for the needy", and the Hadith of Abu Hurairah that the Prophet ﷺ said to Zaynab, the wife of 'Abdullah ibn Mas'ud: (Your husband and your children are the most deserving of those upon whom you spend), and this is taken in its general sense.' And Allah the Exalted knows best.
What is the ruling on one who slept while firmly seated on the ground, regarding nullification of ablution?
The default ruling regarding sleep is that it nullifies ablution. An exception to this is one who slept while firmly seated on the ground; his ablution is not nullified by sleep if he wakes up while still firmly seated on the ground. And Allah the Almighty knows best.