Saudi Arabia becasue it was the Birth and death place of the Prophet and it is where Muslims today get together in order to pray to God and to repect Muhammad
I don't know the Most popular religion. But the most common ones are; Hinduism, Buddhism and Islamic.
Serfs are Islamic
The religion that Muhammad is favored is the Islamic religion. The Islamic religion regards Muhammad as its most important prophet, and pilgrims to sites he visited are important parts of the religion.
Iran
Islamic
Mecca
Mecca is a city in Saudi Arabia that is considered the holiest city in Islam. It is the birthplace of the Prophet Muhammad, and the site of the Kaaba, the most sacred site in Islam. Mecca is central to the Islamic religion and is a destination for the Hajj pilgrimage.
The answer is in your Question: Islam and its followers are called Muslim
Shiites and Sunnis. Refer to question below
Most of the Sunnis believed in the Umayyad's religoin which is the Islamic religion, but the others combined with the Shiites to make their own reglious practices and customs.
Before the Islamic revolution, Islam was still the dominant religion, with most Muslims adhering to the Twelver Shi'a sect. The revolution was mainly to create an Islamic state and to overthrow the Shah, encouraging Islamic Unity.
The largest Islamic country by population is Indonesia. The most important country in the Islamic religion, however, is most likely Saudi Arabia, as this is the area where Islam was founded.