How often can one apply for 144 hr visa exemption to Shanghai

I'm a Canadian citizen. I plan to fly from Japan to Taiwan, and stay over in Shanghai, and then back from Taiwan to Japan and stay over in Shanghai again. Do I qualify for the 144 hr exemption twice?

What are the criteria and necessary documents if I need to apply for a visa to leave the "Shanghai, Jiangsu, and Zhejiang" region.