regarding brake oil level.
If brake pads and brake shoes are new, and brake disc and brake drum are new, then oil level should normally be at max level.
good oil is clear transparentish. any darkness means it has absorbed moisture and should be changed.
as the brake pads and discs and drums start wearing down, brake oil level will go down. it should NOT be topped up.
when new brake pads are to be installed, a C clamp will be used to push the caliper piston inwards to accomodate the new thick pad. this will push oil back to the oil reservoir bottle again making it maximum.
if you had topped up brake oil and then gone for a pad change, pushing the piston back will make brake oil overflow from reservoir bottle. makes a mess.
brake oil is REALLY bad for paint, it will eat it. and when paint is gone metal is exposed, which will start rusting.