Is it a condition for I‘tikaf to be performed in the mosque?
Yes, for I‘tikaf to be valid, it must be performed in a mosque. I‘tikaf is not valid if performed at home or elsewhere.
Is it permissible to include others in the reward of one`s sacrifice?
In the Name of Allah, and may peace and blessings be upon our Master, the Messenger of Allah.
It is permissible for the person offering an Udhiyah (sacrificial offering) to include others in the spiritual reward of the sacrifice. However, it is not permissible for multiple people to jointly share the purchase price of a single sheep or goat, unless one person gifts the money to the other.
It is stated in Mughni al-Muhtaj (6/137) by Al-Khatib al-Shirbini:
"If a person includes someone else in the reward of his sacrifice and slaughters it on his own behalf, it is permissible."
It should be carefully noted that including someone else in the reward of one's sacrifice is completely distinct from offering a sacrifice on behalf of someone else. And Allah the Almighty Knows Best.
Is it permissible to combine and shorten prayers at home before traveling?
It is impermissible to combine and shorten prayers at home before traveling because a person is called a traveler once he/she departs the borders of his/her country, and offering prayer that way was originally intended to exempt a traveler. And Allah 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).