The Simulator browser component is WebKit based and the real device browser is Gecko based. So everything that works on the simulator doesn't work on...
As grift mentioned, it's not possible to fetch phone info from the web app...atleast not locally. The navigator.userAgent returns the proxy server's...
Before submitting it to Nokia store, fill up proper details about Author name, email and version number in your config .xml (if you haven't already)....