2001 Fiesta breather question

[FH42]

Hi ya'll I'm new to this forum and would appreciate if someone can tell me how the valve cover breather/oil filler cap works

I'm the owner of a 2001 fiesta mk4 with the endura 1.3l engine,and I've had it for 9 years now

there is a vacuum line from the intake manifold which connected to the breather which i assume draws the blowby gasses back to the cylinders, and there is another hose from the cap connected to the bottom of the air filter box. is this hose meant to supply fresh air to the breather ?or is it there to draw the gasses back to the intake via the air filter when the engine is under load and there is no vacuum?

another question is how can i tell if the breather works correctly? can it go bad in any way

thank you