Does sacrificing one sheep avail for the entire household?
In the Name of Allah, and may peace and blessings be upon our Master, the Messenger of Allah.
Offering an Udhiyah (sacrificial offering) is a communal Sunnah (Sunnah Kifayah) for members of the same household, provided that their financial maintenance is undertaken by a single provider. By "communal Sunnah," we mean that when one person performs it, the religious recommendation is fulfilled on behalf of the entire household, though the spiritual reward itself belongs uniquely to the one who offered it.
Therefore, if any member of the household performs the sacrifice—even if it is someone who is not legally responsible for the household's expenses, such as the wife or one of the children—the recommendation is fulfilled for everyone in that home. However, the reward does not automatically extend to the other members unless the person offering the sacrifice explicitly intends to share the reward with them—similar to how performing a funeral prayer (Janazah) fulfills the communal obligation for everyone, yet the specific reward is earned by those who actually prayed.
Additionally, a single sacrifice is sufficient for a man who is married to more than one wife. And Allah the Almighty Knows Best.
What are the Sunnahs and etiquettes related to the slaughtering of an animal?
In the Name of Allah, and may peace and blessings be upon our Master, the Messenger of Allah.
1-Avoid terrifying the animal before it is slaughtered.
2-Do not slaughter the animal in front of others of its kind.
3-Offer water to the animal before the sacrifice.
4-Sharpen the knife thoroughly prior to slaughtering to ensure the cut is made as quickly and cleanly as possible. This is in accordance with the statement of our Master, the Prophet (peace and blessings be upon him): "Indeed, Allah, the Almighty and Majestic, has prescribed excellence (Ihsan) in all things. So when you kill, kill well; and when you slaughter, slaughter well. Let each of you sharpen his blade, and let him put his sacrificial animal at ease." (Narrated by Muslim)
Do not begin skinning the carcass until you are absolutely certain that the animal has completely passed away.
Slaughter cattle, sheep, and goats while they are lying down on their left side, facing the Qiblah (direction of prayer). Leave the right leg untied so the animal can move it, helping it rest more easily during its final moments. For camels, however, the preferred method (Nahr) is to slaughter them while they are standing up, with their left knee tied. And Allah the Almighty Knows Best.
What is the ruling on eating or drinking during the first Adhan?
It is permissible to eat and drink during the first Adhan because it takes place before the break of dawn. The purpose of this Adhan is to notify Muslims of the approaching dawn so they can prepare to stop eating when they hear the second Adhan.
Is it permissible to give Zakah (obligatory charity) to one`s poor sister, or brother?
It is permissible for one to give the Zakah to his poor sister, or brother if providing for them isn`t due on him, and the sister doesn`t receive sufficient provision from whomever that is due on. And Allah Knows Best.