US - Shanghai - Country C (one of 53 qualified countries other than US)

Question 1)
I'd like to verify buying one-way ticket to Shanghai from US (nonstop) is okay as long as I have another one-way ticket to country C with confirmed seat and date, flying out within 144 hours. I wasn't sure whether I'm supposed to buy a multi-city airplane ticket and extend the layover in China to be eligible for 144-hour visa-free transit in China.

Question 2)
Assuming your answer to Question 1 is yes, can I buy a one-way ticket from Shanghai to US that has a stopover in South Korea? Although the final destination is the US, I'm technically flying to Country C from Shanghai.

US > Shanghai (nonstop)
Shanghai > South Korea > US

Will above itinerary be eligible for 144-hour visa-free transit?