Hi Andovnas
15 days Switzerland will make a beautiful vacation.
The Swiss Travel Pass entitles to free travels on almost all public transport to, in, and around inhabited places in Switzerland. For many mountain railways, funiculars, lifts, and cable cars, it offers a 50% reduction. Please see the map in order to know where it allows free travel and where you need an additional ticket: https://www.mystsnet.com/en/download/area-of-validity-swiss-travel-pass-2022/?wpdmdl=42165&masterkey=616edeec5609d
Seat reservation is neither mandatory nor required on any regular Swiss train, unless you travel with a party of more than 10. For the panoramic trains, such as Bernina Express, the Glacier Express, the Gotthard Panorama Express, the Golden Pass Express, however, a seat reservation is either mandatory or recommended. You can make seat reservations with the train operator directly. Look up train schedules, or better, any public transport connection here: www.sbb.ch/en or simply download the SBB Mobile app which assists you as your digital travel agent. In the connection details, you will see whether a train requires seat reservation, look for the R.
As a general advice, do not buy mountain tickets (e.g. to Jungfraujoch) in advance. The weather in Switzerland is often changing day by day; there is no point in visiting a mountain top while ending up in clouds, it is a waste of money. Always buy mountain tickets on the excursion day, ask locals about the weather and their recommendation. It will save you money.
If you want, you can list your itinerary here. We are happy to give advice in order to put your destinations in a logical sequence without to too much backtracking. I also suggest the TripAdvisors’ Switzerland forum, there are many volunteers, locals (I am one of them), who can help you draft your itinerary to make the best out of your 15 days. Come back here if you have further questions on tickets and public transportation in general; here we are the ticket experts.
Happy planning.
Best regards,
Roland