Actually the "retraction" of the pads is mostly in the caliper seal. When you
step on the brakes the piston is pressed forward a couple of thousandths of an
inch so the pads press against the rotor. This minor movement is not the
piston moving in relation to the seal, but rather the piston seal distorting
just a bit to allow this very minor movement.
Take you foot off the brake and the seal returns back to normal. Of course as
the pads wear the piston does have to move outward.
As far as the chamfer on the pads go that is for noise prevention. Back in the
days of square cut pads when we had a noise complaint we would chamfer the
leading edge to make them quiet. Finally the pads makers started doing that
from the get go
A normal disc brake will have a bit of drag when rotated and it won't be even
all the way around. Expect a scritch-scritch sound maybe 1X per revolution.
This is stone normal. If the other wheel has no sound when turning that wheel
might be the issue perhaps a loose wheel bearing or warped rotor
Sent from my iPhone