Not exactly .. some domain names are in reality PR1 and when you check theme you find PR4 or PR5 .. So it depend ...
No, you could own a PR9 site and hijack the PR from a PR0 site and show as PR0. However no one in their right mind would do that, people fake PR to increase the value of a site, not to decrease it. With that said, it's not a given that it's really a PR0.
maybe when you get rid of the cloaking script on your domain, you can find out for sure what's the real PR...
the below is a good site for verifiying the PR of a site. http://www.database-search.com/sys/pre-check-en.php Hope it will help you Ani