How to tell the left and right drilled and slotted rotors?
There is no backwards or forwards.It's a preference thing.People will tell you the pads bite harder if the curves are facing the front of the car.
Can you turn the rotors?You can turn them.It works the same as turning any other thing with an interrupted cut.
The left and right stock rotors are the same.Vent blades are straight from the outside to the inside.The fins are not straight.
When braking, cross-drilled and slotted rotors tend to make noise.A small popping noise is normal, as this is the sound of the pad going over the slots/holes.Unless you have full race brakes, a squealing sound is not normal.