I'm traveling from the US, with passport, and stopping in Shanghai for 3 days

and then traveling to Okinawa for 4 days. I will then be flying home from Okinawa to PVG, and then using a different airline ticket (3 hour layover) from PVG to Boston (US). What do I need to get in order to stay in the country for the 1st 3 days, and then stop over on my return flight? Will i apply for a 72hr visa free visit, and I wont need anything for the 2nd stop since i'm not leaving the airport? Or will i need something special for the return trip home?

thank you