Can a US citizen get a 10 year Chinese visa in Nepal?

I am a US citizen currently visiting Nepal. I want to apply for a Chinese one here.

Also what will I need to apply in Nepal besides the application & photo? I plan on flying to Hong Kong, then traveling overland in PRC for a few months, and then leaving overland via Vietnam so I won't have round trip tickets. I haven't planned my itinerary yet so I don't know how long I will be in each place and haven't booked hotels just yet. Do I need to have them booked for the whole 2-3 months ahead of time? Will I also need an invasion letter?
Thanks