1.) There are many setting in the book, but the two main settings are Kabul, Afghanistan; California, and the United States.
2.) Social Classes-
Amir- Amir has a privileged upbringing. His father, Baba, is rich by Afghan standards, and as a result, Amir grows up accustomed to having what he wants.
Hassan is a servant (and Baba's son)
While living in Afghanistan, Baba is a rich and well respected member of his community. Life in America isn't quite as afluent; in America he works at a low paying job as a gas station attendant and lives modestly.
Ali is Baba's servant and Hassan's father figure.
3.) Amir's father pays him little attention, and in much of the novel, Amir seeks to gain his attention. Ali however, is Baba's illegitimate son and Amir's best friend. Baba is far more gentle with Ali and shows him far more affection. This is the main cause of any conflict between the two boys.
4.) Amir fails to intervene in Hassan's rape.
5.) They're best friends, although Amir always feels a sense of competition with him over the affections of their father. Their relationship changes drastically after Hassan's rape.