Just buy at the entrance booth. Yes you have to provide your passport. There are special rates for those above 60 years old and student price if I remember it right. Have fun!

Hi! I would simply take a taxi. They're easy to find and affordable. Or the slow scenic exhausting route is to enter through the east and then take various bus routes, walking etc. across the national park at the top, but that could easily take half a day.

I would say Avatar mountains, because it's a bigger area with more views, so you're more likely to see something if it's foggy as is often the case. We spent a whole day walking around the top of Tianmen but it was raining as usual etc.; we barely saw anything and it was very exhausting. (Still well worth it though for those who have the time.)

you can buy at entrance, it's modern & computerized

U should spend half day in Tiamenmountain then move to wulingyuan area to stay. So easier to explore zhangjiajie national park. Take entrance B of the park.this the best route to explore park in one day. Ending with avatar then bailong elevator (all main scenic in park). Then 3 rd day you can visit baifong lake and grandcanyon. Please check entry schedule and how to purchase ticket of all places.this is so tricky to arrange ur scheduled. We spent 4days to visit all.

a guide told me that it's opened from 7 - 19h in June

Traveling from Wulingyuan to glass bridge by bus will take 1 hour each way. Getting to Avatar viewing point from entrance and back - near an hour each way. The park is one of the most beautiful place in the world & it deserves not less than 2 days of your attention & admiration. If you like to visit glass bridge add one more day for it. Bus from airport in Zhangjiajie to Wulingyuan will take 1,5 hour + half of an hour is taxi to bus station.