About is more commonly used, while on is generally applied in some professional topics.

Actually, should is used here to show a feeling of surprise

Actually, not much of a difference. The first sentence is closest to the meaning: Heilong Jiang is one the northernmost provinces of China. While the second one just indicates that Heilong Jiang is the northernmost province of China.

Hello, Regina. I'm a native Chinese speaker. Would like to be a language partner with me？

Hi, Catherine. I'm a native Chinese speaker. I'll be happy if we can help each other.

出去之前确认一下所有的灯都关了。[Audio]

If you change "if we are able to" into "if we were able to", would is better. Otherwise, you should use will.

"to" is the best choice, I think. It means she respects her parents very much.