Since there's a lot of us out there and nobody has seen every single zoo out there, you will likely get multiple answers for your first question. For #2 it is possible, but only for certain animals. At my home zoo, the Lemurs and Siamangs live on islands so there's no cage or fence. You can't keep most carnivores without a fence or cage, especially the larger ones like lions and tigers. #3...yes, many zoos do actually try to more accurately replicate an animal's natural environment, but the exhibit designer may not have the resources from the zoo they've been hired by to go to Japan or Australia so they probably rely on Internet images. #4 you've already gotten answers from your question you already asked. #5. There's quite a few American zoos that have a moat design for some of their exhibits, the Phoenix Zoo and San Diego Wild Animal Park (aka Safari Park) are two examples. At the Phoenix Zoo, the Cheetahs and African Painted Dogs have a water moat and the Lions and Spotted Hyenas have a dry moat.