Please answer the following questions and make sure to cite your sources correctly.
1. How did Islam expand beyond Arabia and what were the main modes of this expansion in different regions?
2. How did the pilgrimage to Mecca serve as an important religious symbol beyond its narrow ritualistic meaning and function? 
3. What were the factors that led to the decline of the Ottoman Empire?
4. Why is Abu Hamid al-Ghazali often blamed for causing the decline of the Islamic intellectual tradition?