Can i obtain VOA?

HI!I have dual citizenship: Russian and USA citizen. I would like to visit Hong Kong, Hainan, Pearl river region and Tibet. I know that I need to join an organized tour for Tibet. Do I need for China mainland for this trip? Can it be obtained on arrival? where to enter the country then? If it's possible for some of the regions, point what is extra, please! I'll be traveling with my friend, who is USA citizen.Thank you!