What should a person who doubted having missed a pillar of prayer do?
All praise be to Allah, The Lord of The Worlds. The prayer of one who doubts having missed one of its pillars is valid, and nothing is due on him/her since having a doubt after offering the act of worship doesn`t undermine its validity. And Allah Knows Best.
Is it permissible for a woman in her menstrual period to recite from the Mus-haf (copy of the Quran ), or to recite by heart?
A menstruating woman is permitted neither to recite nor to touch the Quran according to what Ali Bin Abi Talib (May Allah be pleased with him) reported about the Prophet (PBUH) who was only held from reciting the Holy Quran by Janabah (Major impurity) [Al-Tirmizi in a sound Hadith]. Although Janabah and menstruation are major impurities, a menstruating woman is permitted to supplicate Allah (Duaa`) and make Zikr (Tasbihat ), even if these involved saying words from the Holy Quran, provided that she does not mean the words for themselves but as a supplication, or Zikr. Moreover, she is rewarded for not reciting the Quran during her menstrual period because she abided by the injunctions of Allah.
What is the validity of the formula for sending blessings upon our master Muḥammad ﷺ: *"Allāhumma ṣalli wa sallim wa bārik ‘alā sayyidinā Muḥammad wa ‘alā ālihi, ‘adada kamāli-Llāhi wa kamā yalīqu bikamālihi"* ("O Allah, send blessings, peace, and grace upon our master Muḥammad and his family, by the number of Allah's perfection, and as befits His perfection")?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah ﷺ.
It is permissible to send blessings upon our master, the Prophet ﷺ, using the formula mentioned in the question, since sending blessings upon the Prophet ﷺ is an act of devotion legislated in its basic essence, without a specific prescribed wording required outside of the formal prayer itself. It is therefore valid to perform it outside of prayer using any formula. This particular formula involves multiplying the blessings sent upon the Chosen Prophet ﷺ to the number of the perfections of Allah, the Exalted — which are limitless — so that, by Allah's permission, its reward and benefit never cease.
The meaning of "the number of Allah's perfection" is that it is without limit, making the blessings sent boundless, corresponding to His perfection, Glorified is He, which cannot be enumerated or counted. This formula is analogous to the words of our Greatest Prophet ﷺ, as related in the authentic ḥadīth narrated by Imam Muslim: the Prophet ﷺ said to Sayyidah Juwayriyyah (raḍiyallāhu ‘anhā): "Indeed, I said four phrases after you [left], three times, which, if weighed against everything you have said since this morning, would outweigh them: Subḥān Allāhi wa biḥamdihi, ‘adada khalqihi, wa riḍā nafsihi, wa zinata ‘arshihi, wa midāda kalimātihi" (Glory be to Allah, and praise be to Him, by the number of His creation, by His pleasure, by the weight of His Throne, and by the extent of His words). And Allah, the Exalted, knows best.
What is the ruling of Islamic Law on a person who abandons prayer after reaching puberty—is he required to make them up?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah.
Making up missed obligatory prayers is an Islamic duty just as performing them in their proper time is obligatory, and taking care of them takes precedence over performing voluntary prayers. This is established by the practice of our Supreme Prophet (peace and blessings be upon him) when the polytheists distracted him on the Day of the Trench from performing the Asr prayer, so he made it up afterward, as well as the Hadith: "Pay Allah what is due to Him, for Allah is most deserving of fulfillment." (Recorded by Al-Bukhari)
Furthermore, it is valid to make up missed prayers at any time.
Whoever has missed a number of prayers and does not know their exact count, it is obligatory upon them to sincerely repent and exert their utmost effort to estimate their number. If they are unable to determine the exact count, they should base it on what is most probable according to their best judgment. They should then make them up gradually; if one performs one missed prayer alongside every current obligatory prayer, the matter becomes easy and manageable, and with the passage of time, one will complete what is owed, Allah willing. And Allah Almighty knows best.