Some pressure vessels (high-pressure reaction kettle, gas cylinder, etc.) are often used in the laboratory. Which of the following statements are correct?

A、Do not remove the pressing bolt with pressure.;

B、When gas cylinder bolts are frozen and can’t be unscrewed, they can be roasted over fire.;

C、Install shock-proof gaskets, when moving, storing, and replacing gas cylinders.;

D、Students use cylinders without training and without the presence of a teacher.