What is the correct point at which to raise the hands when standing up for the third rak‘ah (after the middle tashahhud)?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah ﷺ.
Raising the hands while saying the takbīr [when rising for the third rak‘ah] is a recommended sunnah, and omitting it does not affect the validity of the prayer. The proper time for this is after rising from the middle tashahhud, once one has fully stood up.
It is stated in I‘ānat aṭ-Ṭālibīn (Vol.1/P.158): "His statement, 'and rising from the first tashahhud' — meaning, this manner [of raising the hands] is also a sunnah when he rises from the first tashahhud, that is, when he stands upright from it.
Consider [the question]: when precisely does the raising of the hands begin? Is it at the very start of rising from the first tashahhud, or after he has reached the minimum position of rukū‘ [i.e., once fully upright]? The apparent, [correct] view is the latter — even though the outward wording [of the text] might suggest the former — because at the very start of his rising, he is still relying on both hands [to push himself up, and therefore cannot yet raise them]."
It is stated in ‘Umdat as-Sālik (p. 53): "If his prayer extends beyond two rak‘ahs, he sits after them in the iftirāsh position, recites the tashahhud, and sends blessings upon the Prophet ﷺ alone, without [mentioning] his family [at this point]. He then stands while saying the takbīr, supporting himself with his hands; and once he has stood upright, he raises them level with his shoulders." And Allah, the Exalted, knows best.
Is it a condition for I‘tikaf to be performed in the mosque?
Yes, for I‘tikaf to be valid, it must be performed in a mosque. I‘tikaf is not valid if performed at home or elsewhere.
What is the ruling on the ablution of one who washes his arms from the wrist to the elbows?
In the school of Imam al-Shafi'i (may Allah have mercy on him), washing the arms (hands) is achieved by washing the arms completely, from the fingertips to the elbows. Washing only the palms at the beginning is insufficient, as washing them at the beginning is a Sunnah, but after washing the face, it becomes obligatory (fard). The person performing ablution must wash his palms along with the arms after washing the face. If he does not wash his palms, his ablution is invalid and not correct. And Allah the Almighty knows best.
What is the ruling on the ablution of one who touches women prohibited to him by a temporary prohibition (mahram bi-hurma mu'aqqata)?
It is prohibited to touch a woman who is temporarily prohibited (meaning one whom it becomes permissible to marry after the impediment is removed, such as the wife of a brother or paternal uncle). Touching her without a barrier invalidates ablution. And Allah the Almighty knows best.