Yes. Full implants can replace all the teeth in the mouth for edentulous (toothless) patients, or single implants can replace one tooth. Implants can also replace a few missing teeth that are consecutive, or single implants can be used to replace missing teeth in different parts of the mouth.
With regular brushing, just like natural teeth. A mild, non-abrasive toothpaste should be used to prevent scratching or damage to the surfaces of the crowns.
Because implants fuse to your jawbone, they become a permanent part of your mouth. Implants can be damaged just like real teeth can, but with proper care, it is possible that they can last for your entire life.