Is it possible for every family in China to live in a single-family house with a garden pool like in the US, Canada and Australia?

No way! China is too densely populated, and its land area per capita is too small. There are many areas in China that are simply not suitable for human survival, such as high sea level areas, desert areas, Gobi areas, and so on. There's not much land left, yet it's for over 1.3 billion people to survive, and there's no second example of this in the world.

Not to mention China, France, Britain, Germany, Japan, Singapore, these countries are developed, right? They are also the same as China, the vast majority of people are living in tall residential buildings, there are only a very small number of rich people who have single-family houses.

Beyond that, the kind of single-family homes in the United States, Canada, and Australia are called houses, which directly translates to "house," which is not the same thing as the "single-family homes" you're talking about. Many foreign houses are actually very simple, for example, in Canada, the house is all made of wood, some of the old house is twisted, it looks like a construction site was abandoned the old shed.