Yes, but it is rare.
Police can pull a person over for numerous things such as speeding, no taillights, a headlight out, or swerving.
A citizen can not pull over a police officer for bending the law, but you can report them to the superiors of their Police Department.
Of course, if you violate the law twice
Effectively, yes. A routine traffic check is enough reason to pull you over.
Yes, a police officer can pull over multiple vehicles at once.
Means the police made you pull over in your vehicle.