Hello
Zauchostez26 Will the Swiss Travel Pass cover this entire trip or do we need to buy a ticket for the part of it that’s in Italy?
Swiss Travel Passes are valid until Tirano. Please note that seats reservations are now also recommended on regional trains during peak periods:
https://www.rhb.ch/en/tickets/bernina-line-reservations/
Zauchostez26 For the second train from Tirano to Lugano, is it correct that we have to buy entire train tickets?
Yes. You must buy entire tickets from Tirano to Chiasso (border station).
Zauchostez26 If yes, do we need to do so in advance or can we just buy them at the station the same day?
You can buy the tickets at the station (usually on vending machines). In Italy, tickets for regional trains must be stamped before boarding, you will find devices to do this.
I suppose that you will change in Monza and continue with the RE80, no reservation is necessary or even possible.
Zauchostez26 Also, if we buy 2d class Swiss Travel Passes can we upgrade on particular trains to 1st class?
Yes, it is possible. In some trains you can buy the class upgrades in the train, in other ones it is not possible. So it is better to buy the class upgrades before boarding. You are entitled to buy half fare upgrades for a specific leg or day upgrades (50 CHF).
Kind regards
Danhiel