<<"What should I do within those 4 days and how to travel? I am confused regarding which railpasses to get as I also need to travel from Switzerland to Austria as well on the train. Please guide me on locations to go within 4 days for 2 first time adult travelers.">>
Welcome to the Forum. It is flattering to assume that we know as much as you do about your travel interests and needs. We don't, however. To help us all to be better organized, here are some tips:
Look that over and think about what you would like to do.
Will you be jet-lagged when you arrive? will you be in a time zone more than an hour or two different from the one that your body clock is adjusted to?
If your inteests take you to the eastern part of Switzerland, and you are traveling by train, you may wish to have yuor last overnight be somewhwere in that general direction if you are traveling by car or train. If you are flying, perhaps Geneva would make sense.
So- by what are you traveling. Train? Car? ......Plane?
You have three nights in Switzerland. Lucerne has enough variety in the city , the lake, and the nearby mountains and valleys to make it base for the whole trip. When you leave, if you are flying, Zürich Flughafen is one hour 03 minutes, or one hour 11 minutes from Luzern.....two trains per hour. The ones departing at xx11 have no changes. The one at xx35 stop at Zürich main station, where you could transfer to the train for Venice. The fastest trains are at 1235 and 1425, for a 10 hour journey (approx.)
Yu could also go directly to the Jungfrau region possibly including a few hours in Luzern. Since many of the things worth doing around the Jungfrau depend on good weather, you may wish to have flexibity considering which day to go up, so that you can avoid clouds.
Let us know more about what you like t do. There are a couple of superb museums of works by Klee and Picasso in Luzern, for example. Do you really want to hike?
Go up on mountains?