What is the ruling of Sharia on marrying a Jewish woman, dealing with the Jews, and going to Israel?

What is the ruling on singing and listening to it while accompanied and unaccompanied by musical instruments?

Singing and listening to it unaccompanied by musical instruments is permissible as long as it isn`t practiced as a profession and is done by a man to other men, or a woman to other women with maintaining that no temptations are involved. The words of the song should be Islamic, and if temptation was likely to happen, then the singing becomes definitely forbidden. Temptation here means: whatever leads to committing a sin. In Islamic Sharia, singing accompanied by musical instruments such as the lute and the like is forbidden, and listening to it as well. The reason behind that is the fact that the musical instrument itself is forbidden. However, striking the tambourine and singing Islamic songs are permissible in weddings, circumcisions and the like.

Is the `Iddah (waiting period) of the divorced effective from the time the divorce took place, or from the time of registering it at the court?

It is considered effective from the time the divorce took place, and not from the time of registering it at the court.

Is it permissible for a Muslim physician to specialize in GYNECOLOGY OBSTETRICS, and what is the ruling on working as such?

Some fields of knowledge are an individual duty while others are a collective one, and specializing in GYNECOLOGY OBSTETRICS is a collective duty. However, if there were female physicians to treat women, then there is no need for a male GYNECOLOGY OBSTETRICS specialist to look at women`s Awrahs (private parts) except in necessary situations since the jurisprudential maxim says:” Necessity must only be assessed and answered proportionately.”