SEO for web apps
akronim: I'll take a quick stab at it:
1) hopefully that's landing pages.  You don't have to worry about SEO on the internal pages that google can't see.
2) no, since I assume they just all redirect to the login page, and you want people to be able to find that i guess
3) pick one and 301 redirect to the other
4) Not if the pages can be found via links.  Probably not that useful unless you have frequently updated content like a blog might.