Is everyone obligated to follow the fatwas of his country, and if we adopt the fatwas of scholars of other countries, is it considered a sin?

: It is permissible for one who do not specialize in Shari `ah sciences to apply the opinions of renowned scholars whom he trusts ,whether they be from his own country or not ,but if the scholars don`t arrive at a consensus concerning a certain matter then he must consult someone who is more knowledgeable than himself .It is preferable that you(the inquirer) specify the case of your interest ,so that we could give you a more specific answer since some scholars deliver fatwas based on atypical opinions which should not be applied no matter what .And Allah ,The Exalted, knows best.

If the Prophet (PBUH) was an Arab citizen in 2009, born in an Arab country ruled by an Arab ruler, saw what was happening to Gaza, what would he (PBUH) have done?

What should a woman who is in a state of menstruation, or confinement do if she became ritually pure during the day of Ramadhaan ?

If she became pure during the day time of Ramadhaan, it is desirable for her to fast the rest of that day, and to make up for it along with the days that she had missed due to menstruation.

Is it permissible for a person to sever ties with his sister because her husband had quit prayer and done him harm?

A sister is a blood-relative and maintaining blood-relations is mandatory in Islam. As regards her husband, he should be invited to the way of Allah with wisdom and beautiful preaching.