What is the ruling on performing Tarawih in sets of four rak‘ahs with only one Tasleem?
It is not permissible to combine more than two rak‘ahs with a single Tasleem in Tarawih prayer. Whoever does so, their prayer is invalid. Shaykh al-Islam Imam Muhammad al-Ramli (may Allah have mercy on him) stated: "If a person prays four rak‘ahs of the Tarawih prayer with a single Tasleem, it is not valid if they did so intentionally and with knowledge [of the prohibition]. Otherwise, it becomes an 'absolute voluntary prayer' (nafl mutlaq); because it is contrary to what has been prescribed." [Nihayat al-Muhtaj, Vol.2/P.127].
Must a person refrain from eating for the rest of the day if they break a fast of a vow (nadhr) or a make up fast (qada)?
Whoever observes a vowed fast (nadhr) or a makeup fast (qada) is prohibited from breaking it without a valid excuse. If they break it without a legitimate reason, they are sinful.
However, they are not required to refrain from eating for the rest of the day, because such restraint is only required out of respect for the month of Ramadan, not for other types of fasting.
What are the valid excuses for abstaining from congregational prayer in the mosque?
Praise be to Allah, and peace and blessings be upon our Master, the Messenger of Allah.
Concessions (Rukhsah) are granted to abstain from congregational prayer in the mosque due to general excuses, such as: rain that causes hardship in going out, strong winds at night, heavy mud that cannot be traversed without the risk of soiling oneself, hot winds, and extreme heat or cold. There are also specific individual excuses, such as: illness that makes walking as difficult as walking in the rain, severe drowsiness, evident hunger or thirst, the suppression of bodily wastes (urine, stool, or gas), and fear for one's life, limb, physical faculty, wealth, or honor, among other valid excuses. And Allah the Exalted knows best.
What is the ruling on the follower`s prayer if the Imam stands for a fifth rak`ah?
Praise be to Allah, and peace and blessings be upon our Master, the Messenger of Allah.
If the Imam stands up for an extra unit (rak‘ah) of prayer out of forgetfulness, he must return to the sitting position as soon as he remembers, and he should perform the prostration of forgetfulness (Sujud al-Sahw). It is the duty of the congregants (Ma’mumin) behind him to remind him. However, if the Imam is in a state of doubt regarding the extra unit (and not certainty), it is not permissible for him to return.
As for the congregants: anyone who is certain that the Imam has stood for an extra unit is forbidden from following him. In this case, the follower has two choices: either intend to separate from the Imam (Mufaraqah) and finish the prayer alone, or wait for the Imam in the sitting position and perform the final salams with him—the latter being the preferred option. If a follower knowingly follows the Imam into an extra unit, their prayer becomes invalid. However, if a follower is in doubt and not certain of the mistake, they must continue following the Imam, as the Imam was appointed to be followed.
It is stated in Al-Majmu’ (Vol.4/P.145): 'If [the Imam] stands for a fifth rak‘ah, the follower should not follow him, even if it is assumed that the Imam might have omitted a pillar from a previous unit; because if the reality is known, following him is impermissible since the follower has certainly completed their own prayer. Even if the follower had missed a previous unit (Masbuq) or was in doubt about performing a pillar like the Fatihah, and the Imam stood for the fifth, it is not permissible for the latecomer to follow him in it. This is because we know that this unit is not counted for the Imam and that he is mistaken in performing it.' And Allah the Exalted knows best.