Paris to Zurich Travel and getting around in Switzerland

We are a family of 4 (2 Adults and 2 Children aged 7 and 11) . We are planning to travel from London to Paris (3 nights in Paris) and then travel to Zurich and cover some good tourist destinations in Switzerland. I have my Paris itinerary sorted. Can some one please help answer the following regarding my Switzerland visit ..?

1. What rail pass should I consider buying for travelling from Paris to Zurich..?
2. With this pass, can I travel within Switzerland ..? I am planning to visit (a)Rhyne Falls (b)Mt Titlis (c)Lucerne (d) Interlaken. If not which pass should I go for ?
3. To cover these above 4 places, is it good to find accommodation in Zurich and travel to these places..? If not what are the other options.
4. If I have to travel back to London from Switzerland, is it cheaper to travel from Zurich or Geneva..? And how..?

Thanks in advance.

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