Will an [iOS reinstall](https://superuser.com/a/13345/98033)

 1. Work on any jailbroken-iPhone and
 2. Make a jailbroken-iPhone "unjailbroken"?
 3. Make a jailbroken-iPhone "supported by Apple"?

Similarly, does such an iOS reinstall reset the iPhone (jailbroken or not) back to a "clean, factory default" state?

My near-term purpose: I have an iPhone 4S running iOS 5.1 I'd like to jailbreak to at least install better Google Voice integration like [GVIntegrated](http://thebigboss.org/gvintegrated-a-new-way-to-google-voice).