Can I start fasting based on the moon sighting of another country?
You must follow the moon sighting of the country you are in.
Is it valid to perform the obligatory prayer while sitting?
Praise be to Allah, and peace and blessings be upon our Master, the Messenger of Allah.
Standing (Al-Qiyam) while having the ability to do so is one of the pillars (Arkan) of the prayer; the obligatory (Faridah) prayer is not valid without it. However, whoever is unable to stand may pray sitting down. As for voluntary (Nafilah) prayers, it is permissible to pray them sitting even if one is able to stand, but the one sitting receives half the reward of the one who prays standing. And Allah the Exalted knows best.
If someone starts the day sick or traveling while fasting, is it permissible for them to break their fast?
● A sick person who finds fasting difficult is allowed to break their fast, whether they began the day fasting or not.
● As for a traveler:
○ If they were still at home at dawn and then traveled after Fajr (dawn), they must continue fasting unless they experience extreme hardship, in which case they may break their fast.
○ However, if they were already traveling when dawn broke—meaning they had left their town before Fajr—then they are permitted to break their fast. This is what the Prophetﷺ did during the year of the conquest (of Makkah).
What is the ruling on performing ablution (wudu') and ritual bathing (ghusl) with Zamzam water?
It is permissible to perform ablution and ritual bathing with Zamzam water. However, scholars disliked using it for cleaning after relieving oneself (istinja'). And Allah the Almighty knows best.