What will happen if you wear a yellow jacket? I mean, is the yellow jacket given to others by the Qing emperor like a gold medal to avoid death?

A yellow jacket is not the same as a gold medal to avoid death! The yellow jacket is not very effective. To put it bluntly, wearing a yellow jacket is equivalent to your good performance, and the teacher awarded you a certificate of "three good students", which is an honor. Because yellow is for the royal family, wearing a yellow coat represents a very high honor and scenery, but it has no practical effect!