no, adsense and adwords can help u in just making good revenue, for pr u need to get quality backlinks
yes only if the visitor decides to link to you from a web page they own, visitors alone can't get you a higher PR, where did you hear this myth?
I asked google and the answer was no, but you get more traffic anyway. Im not sure if traffic increases PR.
AdSense and AdWords are services that provide script based solutions (AdSense) and traffic (AdWords). They themselves are not sites that provide backlinks to your site. And PR is that - measuring the quality of the backlinks to a particular site.