Who is responsible for performing the aqiqah?
All praise is due to Allah, and may peace and blessings be upon our Master, the Messenger of Allah.
The one upon whom the 'aqīqah is incumbent is whoever is obligated to financially maintain the newborn — whether the father, paternal grandfather, or mother. It is to be performed from their own wealth, not from the wealth of the newborn child.
As for one upon whom the financial maintenance of the newborn is not obligatory, they may not perform the 'aqīqah except with the permission of the one upon whom it is obligatory — namely, the father. And Allah Almighty knows best.
What is the ruling on praying alone (munfaridan) in a row, and what should I do if I enter the mosque together with another person, and there is only a single gap in the first row with no second row present — should I fill that gap in the first row, or should I stand together with him in a new second row?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah ﷺ.
If a person enters [the congregation] and finds no space available in the row, it is recommended for him — after making his opening takbīr for the prayer — to gently pull someone from the row in front of him to pray alongside him, provided he senses that this person would be agreeable to it. If that person does not agree, then he prays alone, and there is no dislike attached to his doing so in that case.
If he ends up praying alone [behind the row], it is sunnah for him to stand directly behind the imam. Then, if someone else arrives, that person stands to his right; and whoever comes after them stands to his left — and so on — such that the imam remains centered in the middle of the row. This is done so that everyone attains the reward of congregational prayer.
As for the case where two people enter the prayer together, and there is a gap in the row wide enough for only one person, then the two of them should pray together in a new row [of their own], and whoever arrives after them should fill that original gap. This is because if only one of the two fills the gap, the other would end up praying alone [which is to be avoided when it can easily be prevented].
Al-Khaṭīb ash-Shirbīnī (raḥimahullāh) said in Mughnī al-Muḥtāj (Vol.1/P.494): "If he does not find space, then it is recommended for him, while still standing, to gently pull a single person from the row toward himself after making his opening takbīr — out of caution, so as to avoid the position held by some scholars that a person's prayer standing alone behind the row is not valid.
Az-Zarkashī and others said: this should only be done if it seems he would agree to it; otherwise, he should not pull anyone — indeed, doing so becomes impermissible, out of fear of causing discord (fitnah). It is recommended for the person being pulled to cooperate and agree, so that he may attain the reward of assisting in righteousness and piety (al-birr wat-taqwā). However, he should not pull one of two people [praying together] from the row, since this would cause one of them to end up praying alone. This is why the 'pulling' described here takes place only after the opening takbīr [i.e., once the person doing the pulling has already validly begun his own prayer]."
Accordingly: it is sunnah for you to pray alongside the person praying alone, and then, if someone else arrives afterward, you may go and fill the gap in the original row. And Allah, the Exalted, knows best.
Can someone who begins a voluntary fast break it?
It is preferable for someone who begins an act of worship not to break it.
Allah the Exalted has said {what means}: "and let not your [good] deeds come to nought!" [Muhammad/33].
However, if a person starts a voluntary fast (nafl) and needs to break it, they are going against what is preferable, but there is no sin upon them.
What is the ruling on praying while wearing shoes?
Praise be to Allah, and peace and blessings be upon our Master, the Messenger of Allah.
There is no sin for a Muslim to perform prayer while wearing their sandals or shoes, provided they are free from any impurities (najasa). It was narrated that Anas bin Malik (may Allah be pleased with him) was asked: 'Did the Prophet ﷺ pray in his sandals?' He replied: 'Yes.'" (Related by Al-Bukhari).
It is stated in Fath al-Bari (Vol.1/P.494) by Ibn Hajar (may Allah have mercy on him): "Regarding the phrase 'praying in his sandals,' Ibn Battal said: 'This is understood to apply as long as there is no impurity on them; furthermore, this is considered one of the legal concessions (rukhas)." And Allah the Almighty knows best.