[1]

Already possible for the whole year.

[2]

No, you won’t need a ticket. Just a reservation. Price depending on time of the year.

p3]

(not asked) It’s possible to go this route without any reservation (and so without any additional cost). There are free regional trains every hour. Even the Bernina Express itself can be used in the front cars without any reservation (but you won’t have panoramic coaches then). 

What does this mean?

If you’d need a ticket, this wouldn’t be available right now. Tickets are available just two months in advance.

But you don’t need a ticket as you are a holder of a railpass and to buy the reservation is possible.

But im travelling in a group so we need multiple reservations, is that possible?

You may do up to nine seat reservations at once. Is that enough?

Yep, but its says “Only one seat reservation can currently be booked for your travel date.” is this wrong or what?

The number of travellers can be changed by clicking on +.

It’s just bad translation. It means “a seat reservation”, not ”one seat reservation”.

Ohh that makes sense, there were some other really weird translations. Thanks for the help!

No problem. Enjoy your trip.

Information from travellers in the Swedish Facebook group for train travellers where I am a member say that it is better to travel in the reservation free coaches of the Bernina Express than to buy reservations. There are less people in the reservation free coaches which makes it possible to move from one side to the other to get the best view of the scenery. 

But they dont have the same panoramic windows I believe.

No, these are simply railcar units like on any other regional train (modern ones from Chur and vintage ones from St. Moritz) pulling the panoramic coaches.

It's also not especially true what people do write in a Facebook group. In your case (I've seen you had a look for 1st class) that would mean that at each end of this railcar there are (just) two groups of seats where you could change sides. The train has to be very empty in july to have the possibility to change sides.

Some people just do love the possibility to open a window to take photos.