Is it permissible for a sick person to pray while sitting on a chair?
All perfect praise be to Allah, The Lord of the Worlds It is permissible for a sick person, who is unable to stand up, to offer prayer while sitting on a chair. If he/she was unable to prostrate while on the chair, the he/she should pray while sitting on the ground, but if he/she was neither able to bow (Roku),nor to prostrate, then he can do them while sitting on the chair. And Allah Knows Best.
What is the ruling on vomiting, and does it invalidate ablution?
Vomit is impure (najis). Its exit is not considered one of the nullifiers of ablution. However, the mouth must be washed and purified from it, and any that gets on clothing or the body must be washed for prayer, because prayer is not valid with impurity present on the body or clothing. And Allah the Almighty knows best.
What should a person, who doubts the validity of his Wudu, or over performs it, do?
One who doubts the validity of his/her Wudu while performing it should redo it until he/she is certain of having attained purity. But, if doubt was after having performed Wudu, then he/she should not pay attention to that as doubt after the end of an act of worship does not count. This is of course in case doubt was within the reasonable limits since once it goes beyond that, it becomes a whispering of the Shaytaan (devil) which he/she should ignore as the Wudu is valid.
What is the ruling on Zakat al-Fitr?
Zakat al-Fitr is obligatory upon every Muslim for themselves and for those they are financially responsible for, provided they possess wealth that is surplus to their and their family's needs on the night and day of Eid.
Ibn Umar reported: "The Messenger of Allah ﷺ made Zakat al-Fitr obligatory—one sa‘ (measure) of dates or one sa‘ of barley—upon every Muslim, whether slave or free, male or female, young or old." [Narrated by Al-Bukhari]
Its estimated amount is approximately 2,500 grams of wheat or rice, and the General Iftaa` Department issues an annual ruling specifying its monetary value.