What is the ruling on wiping the white area behind the ears instead of wiping the head?
The obligation in ablution is to wipe some of the head; it is not a condition to wipe all of it. Wiping the white area behind the ears suffices for that. And Allah the almighty knows best.
Does sacrificing one sheep avail for the entire household?
Praise be to Allah, and peace and blessings be upon our master, the Messenger of Allah.
In Islamic jurisprudence, the sacrifice (Udhiyah) is considered a Communal Sunnah (Sunnah Kifayah) for the members of a single household who share the same financial support.
If one member of the household performs the sacrifice—even if they are not the primary breadwinner, such as the wife or one of the children—the religious request is fulfilled on behalf of the entire household. This is similar to the Funeral Prayer (Salat al-Janazah), where the obligation is dropped for the community if some perform it.
While the communal request is satisfied by one person's action, the specific spiritual reward (Thawab) for the act of worship belongs only to the person who sacrificed, unless that individual explicitly intends to include the other family members in the reward.
A single sacrifice also avails for a man who is married to more than one wife. And Allah the Almighty knows best.
What is considered a woman`s Awrah (parts of the body that must be concealed during prayer) while offering prayer, and is her foot part of it?
A woman`s whole body is considered an Awrah while offering prayer except the hands and the face. Thus, her foot is an Awrah as well. And Allah Knows Best.
Where should a woman who is led by her husband in prayer stand?
All perfect praise be to Allah The Lord of The Worlds It is from Sunnah (Prophetic tradition) that she stands behind him. And Allah Knows Best.