Thank you for your request.
I cannot guarantee that the connection to Tirano will be possible. If there is a lot of snow, it may have delays.
We have a Timetable change on 11 December 2022, it is possible that the departure/arrival times will change a bit. The reservation for the Glacier Express is available 3 months in advance, i advise you to contact us in mid-September on +41 848 44 66 88 (0.08/min.) or, if this number doesn't work, on +41 51 225 78 00.
The Eurail pass is valid for Tirano, you do not need a reservation for the regional train St. Moritz - Tirano,
Have a nice weekend.