Why was the exact date of Laylat al-Qadr concealed?
The wisdom behind this is to encourage Muslims to strive in worship throughout all the nights of Ramadan, or at least in the last ten nights. By doing so, they will earn the reward of observing Laylat al-Qadr as well as the reward of worshiping on other blessed nights.
Is it valid to have Suhoor before sleeping, even if it is before midnight?
Suhoor refers to the pre-dawn meal eaten after midnight to help a Muslim endure fasting. The closer it is to Fajr, the better.
The Prophet ﷺ said: "My Ummah will remain upon goodness as long as they hasten to break the fast and delay Suhoor." [Narrated by Ahmad]
This is because delaying Suhoor makes it more effective in providing strength for worship. However, if there is a risk of Fajr entering while eating, one should refrain from Suhoor out of caution.
The Prophet ﷺ said: "Leave what makes you doubt for what does not make you doubt." [Narrated by Al-Tirmidhi]
If a person enters a mosque and finds the congregation in the final tashahhud, which is more virtuous — joining them or waiting for a second congregation to catch the opening takbīr (takbīrat al-iḥrām)?
All praise is due to Allah, and peace and blessings be upon our master the Messenger of Allah ﷺ.
If a worshipper finds a congregation that is about to finish its prayer, and he hopes to catch the entire prayer from the beginning with another congregation, it is more virtuous for him to pray with this first congregation and then repeat the prayer with the second one — provided he does not intend to confine himself to a single prayer. If, however, he intends to perform only one prayer, then it is more virtuous for him to wait for the second congregation rather than joining the first, so that he may attain the reward of congregational prayer for every single rakʿah.
Al-Khaṭīb al-Sharbīnī, may Allah have mercy upon him, states: "If members of a congregation enter the mosque while the imam is in the final tashahhud, al-Qāḍī Ḥusayn held that it is recommended for them to join him in prayer, and that they should not delay in order to form a second congregation. Al-Mutawallī, however, affirmed the opposite view, and al-Qāḍī's own statement elsewhere supports this latter position, which is the relied-upon view. In fact, it is more virtuous for a person who has missed part of the prayer with one congregation, and who hopes to catch another congregation with whom he can attain the entire prayer within its proper time, to delay so that he may catch it in full with them. This applies when he intends to confine himself to a single prayer; otherwise, it is more virtuous for him to pray with the first group and then repeat the prayer with the others." [Mughnī al-Muḥtāj,Vol. 3/P.186] And Allah the Almighty knows best.
What is the ruling of Islamic Law on a menstruating woman (ḥā'iḍ) reciting the Islamic ruqyah (Qur'anic/spiritual healing)?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah ﷺ.
It is permissible for a person in a state of janābah (major ritual impurity), or a menstruating woman (ḥā'iḍ), or a woman in postpartum bleeding (nufasā'), to recite for the purpose of ruqyah (spiritual/Qur'anic healing), even if this includes some verses of the Noble Qur'an — whether recited from memory or by looking at the Muṣ-ḥaf (the physical copy of the Qur'an) without touching or carrying it — provided that the intention behind the recitation is ruqyah, protection (taḥṣīn), and remembrance (dhikr), not the intention of tilāwah (Qur'anic recitation as an act of worship in itself). This remains permissible even if what is recited is an entire sūrah, such as Sūrat al-Mulk.
Imam al-Khaṭīb ash-Shirbīnī (raḥimahullāh) said: "It is lawful for a person in janābah to utter its [the Qur'an's] remembrances and other content — such as its admonitions, its narratives, and its rulings — so long as it is not with the intention of [reciting] Qur'an. [This is] like his saying upon mounting [a vehicle]: 'Glory be to Him Who has subjected this to us, and we could never have accomplished this [by ourselves]' [Sūrat az-Zukhruf: 13] — meaning, [could never have] been capable of it — or upon a calamity: 'Indeed we belong to Allah, and indeed to Him we shall return'... In fact, my teacher, ash-Shihāb ar-Ramlī, issued a fatwā that even if he recited the entire Qur'an without the intention of [reciting] Qur'an, it would be permissible." [Summarized from Mughnī al-Muḥtāj, Vol. 1/P.217] And Allah, the Exalted, knows best.