No, every sink has its own shutoff valve that you can use. It should be under the sink. You just need to turn the water supply to the sink off.

It might be but it's extremely unlikely. Reach under the sink and feel around the underside of the handle for a nut. Tighten that nut by hand and y...

See the seam where the handle meets the faucet fixture? Slide a flathead screwdriver in that seam and pry the handles up.