"There is also something else I notice: some people will decide they will not understand you because you look/are foreign no matter how hard you try or even if you don't make not many mistakes. There is a famous video about that[1] but this is not limited to Japan, I also saw it in France too with foreigners trying to speak French."

I have encountered this as well. It also happens more frequently from foreigners who have learned English (perhaps even better than your studying of language X) and they just don't want to talk to you in their language.

Fortunately, most people are not like this, and from my experience of both Japanese/Chinese people, they are very open to communicate with you in their language.

With the only exception being that you have to speak a bit more Chinese before English speaking Chinese people will agree to speak Chinese regularly with you, versus Japanese where they will speak Japanese to you from almost day one if you want. (which is a blessing and problem since you won't understand much) haha