Can I go around same day to Shanghai Botanical Garden, Nan Putuo Temple, and Huishan Fortress? Will it be too rushed? And can Taiwanese people buy tickets on-site again?

Early in the morning, go to Nanshu Temple and arrive by 7 o’clock. Your time is sufficient then.
“Lives next to a botanical garden, in the morning at 8am visits the botanical garden; comes down directly takes bus to Nan Putuo Temple and Hu Line Tower; had dinner at Zhennan Village and watched the sea; as long as one has physical strength it’s okay.”
Physical condition is good, no problem. If there are elderly or children, not recommended. Recommended to make a reservation online in advance.
“The botanical garden is quite large, if you plan to explore it all day, you should set out early in the morning. We left at 10am and finished our visit around 4pm.”

When I went to the botanical garden, there were many people waiting in line and taking photos for hours. In the morning, it took a while before noon by multiple times returned, then had to go to Xiangtan Temple before 1 pm, but I’ve already bought an e-ticket online and reserved my spot ahead of time.
That’s a scenic spot nearby, I’d leave early in the morning and go for a day trip. It’ll be quite tiring. I bought all my tickets online; unfamiliar with on-site purchases.
It can, they are all on the same line, not taking a roundabout way.