Hello, Layover Question

I am traveling from Toronto -> Shanghai -> Kunming -> Chiang Mai in Thailand, all in one trip, where the stay in Shanghai and Kumnig are layovers. Do I need any sort of visa at all, If I am just transiting through the two Chinese cities?

Additionally, our airline has arranged a hotel for us before our Kunming to Chiang Mai flight, and so in this case, are we allowed to leave the airport for less than 24 hours to go to this hotel under the 24 hour exemption policy?