Chinese visa

Hello, I'm going to China for 14 day tourist trip in mid June this year organized by travel agency. Soon after i booked the trip, I took a course in chinese language and my tutor said they organize summer camp in Beijing this August so I plan to go. My question what should I look in the visa application to make it for at least 2 entries (for both trips) is there an option to choose the duration of L visa (and number of entries) and what additional documents I need for my application, outside of the required flight tickets, hotel reservation, itinerary? Thank you!