
Hi,
To start with enter puppy only, if your dog is quite a mature puppy when it is around 10 months you could put it into Junior. Any open class is really for mature dogs, whether in the breed classification or any variety classification, and a puppy would not really stand any chance of winning unless it was exceptionally good. Any Variety classes are for any breed, not just your breed. Until you get started it might be better to stick to breed classes. If you decide to enter an Any Variety classes then again put your puppy in AV Puppy. Show schedules have a list of classifications in them somewhere which explain what each class is and who can enter. The brace class is for two dogs shown together, both owned by the same exhibitor.
If you go to a good ring craft class the trainer should be able to explain this to you and to help you with your entries. Is this your first dog for showing? If so ring craft classes are very helpful as they teach the dog what is required for the show ring. Other breeders/owners of your chosen breed might be attending as well and they would probably advise you, on things such as the right type of lead etc... Have you thought of contacting the breeder of your dog? If they show, they will be pleased to help and advise you.
Polly