Is the son of the sister by breastfeeding considered a mahram in Islam, and is it permissible for a woman to go for Hajj with him?
Everything that is prohibited by lineage is also prohibited by breastfeeding. The son of the sister by breastfeeding is considered a mahram, just like the son of the sister by blood, and it is permissible for him to be her mahram for Hajj and Umrah. And Allah Knows Best.
What is the ruling on combining (jam‘) and shortening (qaṣr) prayers when travel is repeated on a daily basis?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah ﷺ.
A traveler is permitted to avail himself of the concessions of shortening and combining prayers once the distance of his journey reaches (81 km) or more. This is on condition that his journey is a permissible one, and that he begins shortening and combining only after setting out and passing beyond the built-up limits of the city in which he resides, or beyond the administrative boundaries of the area where he lives.
Accordingly, if the distance between one's workplace and one's place of residence reaches the distance upon which the concession of combining and shortening depends, then combining and shortening are permissible once he leaves the built-up area, even if this travel is repeated on a daily basis.
Ash-Shirbīnī (raḥimahullāh) said: "It is permissible to combine Ẓuhr and ‘Aṣr, either as an early combination (taqdīm) in the time of the first, or as a delayed combination (ta'khīr) in the time of the second; and likewise Maghrib and ‘Ishā' — either early, in the time of the first, or delayed, in the time of the second — during a long, permissible journey, in following [the Prophet's practice]. As for the delayed combination, it is established in the two Ṣaḥīḥs from the ḥadīth of Anas and Ibn ‘Umar (raḍiyallāhu ‘anhum). As for the early combination, Ibn Ḥibbān and al-Bayhaqī graded it ṣaḥīḥ from the ḥadīth of Mu‘ādh, and at-Tirmidhī graded it ḥasan." [Quoted with slight abridgment from Mughnī al-Muḥtāj, Vol.1/p.529]
The conditions for combining and shortening have already been explained in Fatwa No. 14 and Fatwa No. 842. And Allah, the Exalted, knows best.
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]
What is the ruling on performing istinja' with perfumed tissues or a tissue moistened with water?
Performing istinja' with perfumed or moistened tissues is not sufficient if they are not dry, due to the moisture on them reaching the impurity, which increases its spread rather than reducing it. Then, to remove the impurity, one must use pure water. And Allah the Almighty knows best.