May 8, 2011 - 6:10 AM
As far as I know:
1. Yes, you can use you Swiss Pass to get to Interlaken from Basel, if the train you're in goes as far as Interlaken. Depending on your time of departure you may have to change trains, but the train personnel will know that. On top of that you can check the SBB time table.
4. A Swiss Pass does not completely cover the track to Kleine Scheidegg and Jungfraujoch, you will have to pay extra from Wengen or Grindelwald. Buying a return ticket is possible though, with that you can travel to Grindelwald or the other way around. Just show your Pass at the counter and tell the railway personnel what you want, they will provide you with the right extra ticket. By the way, there's a link to an overview of what you can do with your Pass on the Swiss Pass page.
5. If I were you I would not go and see the Trümmelbach-falls at the same day. It may be doable if you leave very early (in that case starting in Grindelwald en ending in Lauterbrunnen would be better) but it's all rather overwhelming.
6. There are lots of plans and ideas on this website. You can just browse a bit and see if you come across some places and ideas. For me it's hard to give suggestions, as it all depends on what you like to see and do.
I wish you a very pleasant trip en I hope this helps a bit!