Oct 13, 2014 - 5:31 PM
Welcome to MySwissAlps Thurag!
As for your questions: yes, you can visit the Jungfraujoch by train from Interlaken on November 14. All details on this trip can be found in the timetable. There will certainly be snow up there. Please check the page I linked to for more information about the Jungfraujoch.
If you have a Eurail Select Pass that includes Switzerland, it's not necessary to buy an additional rail pass in most cases, as your Eurail Select Pass offers free or discounted traveling on quite some Swiss train routes. This does depend on your exact itinerary though; here's how to check if an extra rail pass would be worth it. The trip Interlaken-Jungfraujoch is 25% off indeed. Please find details, including a validity overview for Switzerland, at our Eurail Select Pass page.
I hope this answers your questions!