Is vomit among the nullifiers of Wudu (ablution)?
Vomit does not nullify Wudu, but it is a Najaasah (impurity) that requires rinsing the mouth and washing whatever became dirty by it since the prayer becomes valid only after the removal of Najaasah. And Allah Knows Best.
Does offering Udhiyah (Offering a Sacrificial animal at Aid Al-Adha) avails from offering Aqiqa?
Offering an Udhiyah doesn't avail a person from offering Aqiqa because each of which is a different act of worship. And Allah Knows Best.
What is the ruling in Islam on castrating animals to use them for work?
All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
This isn`t permissible because jurists said: "It is permissible to castrate the animal if it is eaten and this procedure is done at early age." And Allah The Almighty Knows Best.
I have a question regarding the deferred portion of the dowry (Mahr)*. Is the wife entitled to it only upon divorce or she can claim it even if divorce hasn`t taken place? Moreover, does she have the right to claim this portion after death of husband, even if he didn`t divorce her before that?
All perfect praise be to Allah the Lord of The Worlds. May His blessings and peace be upon our Prophet Mohammad and upon all his family and companions.
In the marriage contract, it is recorded that the deferred portion of the dowry is due upon divorce or death, whatever comes first. If divorce took place first then the woman is entitled to it and if the husband died this amount must be paid from his estate. On the other hand, if the woman died then the husband becomes liable for this portion and it becomes part of the woman`s estate. We advise every husband to give this portion to his wife while alive because it is a right of hers. And Allah The Almighty Knows Best.
* In Islam, a Mahr is the obligation, in the form of money or possessions paid by the groom, to the bride at the time of Islamic marriage (payment also has circumstances on when and how to pay). While the mahr is often money, it can also be anything agreed upon by the bride such as jewelry, home goods, furniture, a dwelling or some land. Mahr is typically specified in the marriage contract signed upon marriage.