Is it permissible for one to shake hands with his uncle`s daughter?
No, it isn`t because he is a non-Mahram (Marriageable) to her.
What is the ruling on speaking while relieving oneself?
It is disliked for one relieving himself to speak while doing so, except out of necessity. And Allah the Almighty knows best.
Should the Zakah (obligatory charity) giver tell the poor recipient that this is the Zakah of his money?
No, he shouldn`t. But, the Zakah giver should make an intention in his heart that it is the Zakah of his money when paying it to the poor. And Allah Knows Best.
What is the ruling on someone who fainted while fasting?
● If a person had the intention to fast from the night but then fainted during the day and regained consciousness before sunset, even for a moment, their fast remains valid.
● However, if they remain unconscious for the entire day, from Fajr until sunset, their fast does not count, and they must make up for that day later.