Various TWOV and frequency

I have a US passport. I have a round trip ticket from Los Angeles to Shanghai with a layover in Hong Kong both ways. I will have a separate round trip direct fly ticket from Shanghai to Incheon, Korea.

1st journey LAX -> HKG -> PVG -> ICN
2nd journey ICN -> PVG -> HKG -> LAX

On the 1st journey, I will be in Shanghai a little over 48 hours. Does Shanghai still have 72-hour TWOV or do I request 144-hour TWOV?

On the 2nd journey, I will be in Shanghai less than 24 hours with an overnight layover. I would like to stay at a nearby airport. Do I get 24-hour TWOV? Will 24-hour TWOV allow me to leave the airport?

Lastly, I will be needing TWOV in Shanghai within 5 days from each other. Will this be an issue? I couldn’t find information about frequency of TWOV eligibility in Shanghai.