The title of the Islamic Empire was Caliphate. The Caliph was called Amir-ul-Momineen.
Caliph (or Khalifa in Arabic)
There is no Islamic Empire.
It depends on the Islamic Empire in question. Assuming that you are talking about the Abbassid Caliphate (which is most commonly referred to as "the Islamic Empire"), the group that brought them down was the MONGOLS.
In 1492 the Islamic Empire finally left Spain but i dont know when it began.
Yes. The Mughal Empire was a great Empire of the Muslims in India.
Ottoman Empire
The Abbasids, as the ones from the Islamic Empire.
Different in different parts of the empire.
Emperor is the title given to the ruler of an empire.
Invasions by the Islamic Ottoman Empire destroyed the Byzantine Empire.
yes
By forming Islamic armies, conquering non-Islamic countries, and making them into Islamic countries. Simple.