The answer to Question 3 will not be answered after the season; it should be answered during the season.
I expect the Twins to sign probably two of their current starters who will be free agents to extensions. Trades are unlikely; everyone wants too much for the best pitchers. And the Twins did not go out and get a top-of-the line free agent starter this winter, and likely won't next winter.
The minors and current non-roster players could fill at least two of the spots for next year; I'm thinking Hendrix and Doyle.
The Twins typically develop ace pitchers and closers; they don't take someone else's, unless a Santana can be had and developed. I would look at Liriano and Baker being signed to two- or three-year contracts during the year. Otherwise, the Twins will continue to develop the horses they have in the pens.