San Francisco - Wuhan - Guangzhou - Kathmandu (Nepal)

Hi

I have a China Southern flight (Flt No. CZ660) from San Francisco (SFO) to Wuhan (1 hr 45 mins stopover - no plane change) then to Guangzhou. 10 hrs 30 mins Transit in Guangzhou then fly to Kathmandu, Nepal (flt no. CZ6067).
Do I need a Visa on hand before boarding at SFO? or one can get Transit visa on arrival at Wuhan airport?

Return flight: Kathmandu (Nepal) to Guangzhou. 5 hr 45 mins transit at Guangzhou then fly to SFO (flt no. CZ659). Again 2 hr stopover (no plane change) at Wuhan before arriving SFO. Since both Wuhan and Guangzhou entertain 72 hr free transit, still have query on this. Do I need an entry permit on hand before boarding at Kathmandu (Nepal)?

FYI: Called china southern airlines number of times, every time they redirected me to check with Chinese embassy. Weird!!!

Would appreciate your help!