Q: What is proper Volvo brake repair procedure?

I bought this car in Aug 2015, with 53000 miles, as a certified Volvo from a Volvo dealer. There has been some vibration in the steering wheel, on braking. In Sep 2016, the dealer said the front rotors need to be replaced, not urgent. On the freeway, had brakes grabbing, not slowing down the car. Took car to a local Fletchers Auto. They said the passenger rotor needs to be replaced, but its pad is at 8mm (said the pad was probably replaced, but not the rotor). They said the rears were at 4-5mm, still okay. They replaced only the front passenger rotor, and reused the brake pad. At first it was fine, drove next day, and there is significant fast vibration in wheel, accelerator. Looked at rotor, there are angled score lines all around the rotor, going from center to outer rim, aimed towards rear of car, about 45 degree angle. Should the pad be replaced when the rotors are? Are front brakes done in a pair, or can they be done individually, on a Volvo?

My car has 83000 miles.
My car has an automatic transmission.