Is it necessary to book trains in the Jungfrau region?

Information
I will be staying in Interlaken with 4 whole days to kill from the 25th of this month.
I would like to do some hiking in the region. For example, getting day-return train tickets to Grindelwald and/ or to Lauterbrunnen.
I would also like to have a trip up to Jungfraujoch.
Questions
Firstly, is it advisable to book (either of) these journeys in advance? If so, how far in advance and by what means?
Extra information
I have read in the "Rough Guide to Europe on a Budget" that to get to Jungfraujoch it is better in their opinion to take cable cars. I am happy to either and so the above questions really apply twice: to trains and to cable cars.
Note: I have an InterRail pass.
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Do I need to book Jungfraujoch in advance?
You don't need to reserve or book in advance for trains to Jungfraujoch, you can just turn up, buy a ticket at the station and go. In fact, I recommend buying a ticket on the day so you can check the weather before deciding to go - check the webcam on www.jungfrau.ch.Do you need reservations for Jungfrau?
For the journey to the Jungfraujoch, we strongly recommend a paid seat reservation in good weather.Is the Jungfrau train worth it?
Is Jungfraujoch Worth It? That depends. All in all, it's a great experience. You get to see stunning alpine views and the Aletsch Glacier, which is located in the Jungfrau-Aletsch Protected Area, a UNESCO World Heritage site.How much is the Jungfrau railway?
Summary of Jungfraujoch Ticket OptionsPriceWhere to buyRegular ticket ex LauterbrunnenCHF 221.60^BUY HERERegular ticket ex GrindelwaldCHF 214.00^BUY HEREGood Morning TicketCHF 175.00At local stationDiscounted ticket with Jungfrau Travel PassCHF 74.00^At local station8 more rows•Nov 11, 2021Planning to travel to Jungfrau, Switzerland? | Top 3 Money Saving Tips | Tips to get the best deal!
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