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Im not sure your really in the right place for that kind of question (its not really SEO related, more technical web development) To point you in the right direction though, stackoverflow is a good resource for development questions: http://stackoverflow.com/questions/14520036/how-to-detect-user-is-on-a-mobile-device-and-offer-app

I found no examples, sorry... I don't understand your comment about rel=canonical.  There should be ONLY ONE rel=canonical, and it should reference its own page, EXCEPT in the rare case I outlined above where the content on two different country pages is essentially identical.

If you interlink a bunch of your own sites like this and make a few thousand links, you'll get a penalty.  You're begging for one under Google's link schemes guidelines. We've had several clients who had "maps" with all their locations in the map and all the links going between each site.  It can create a few thousand (or a few hundred thousand) links very quickly. If you're going to do this, at the very least make them no-follow.

Reagrdless of external or internal. lets say you have 4 links Link 1 goes to page A Link 2 goes to page B Link 3 goes to page C Link 4 goes to page C Lets leave out that the first lionk passes a bit more then the second, page C will get 50% of the PR. But it will only get the link text relevancy of the first link to it. But if you linked to page C like this pagec.html#someAnchor and pagec.html#someotherAnchor then you will get the link text relevancy for both links