There are about 900 breeds of sheep in the world.
Judges are generally certified to judge one or several breeds, usually in the same group, but a few "all-breed" judges have the training and experience to judge large numbers of breeds.
The sit for exam is a modified version of the Stand for Exam. It is generally used in novice level classes and requires the handler to order the dog to sit and then to move away from the dog the length of the leash. The judge will then approach the dog and pet the dog's head.