@sailorgirl; the answers to your questions have their origins in what happened to China immediately before, during and after the Opium Wars and of course its invasion by Japan - that in the context of current threats being made on a daily basis against China by western powers including the USA, the UK and Australia.
There's no doubting that China regards places including Hong Kong and Taiwan as Chinese territory, along with much of the South China Sea.
US World Map Showing China: 1776AD
It's my perception that China would have preferred a less aggressive and more evolutionary model of transitioning to a better future. What's happened in Hong Kong and the decision of countries including Australia to selectively discriminate against Chinese companies and to denigrate China in global forums has rattled China's cage to the point where it feels a need to push back.
