The safavid empire trained Christian boy to fight in their empire, and that helped improve their military. The Christian boys were given honor and respect.
The Safavid, Mughal, and Ottoman empire were the first ever gunpowder empire to ever exist. Prior to them using gunpowder as a form of weaponry, China used it for entertainment in the form of firework.
Sunni and Shi'a are both part of the Islamic religion. They split into different group after the death of Muhammad, the prophet. They divided because they disagreed on who was going to rule after Muhammad, and they have been fighting each other ever since.
This was a system established by the Inca in order to construct roads and create buildings throughout the empire. This required the natives to work rigorous hours and made many of the natives upset.