Do not buy seat reservations in Switzerland. They're optional and a complete waste of money. Trains are frequent and have capacity. Around midday they'll basically be empty.

You don't need to do anything, simply add the journey to your pass and hop on the train.

I believe you're going to Vaduz ? It will be quicker to take the train to Sargans and then a frequent bus (line 12/12E). Buses are not included in the pass.

The bus costs 8 CHF for a ticket valid 2 hours or 12 CHF for a day pass in the whole country. Please use sbb.ch or SBB app to buy those tickets.

Thanks! For the Super Saver Pass you suggested that I buy for the next day to go from Liechtenstein to Murren, can I buy that the day of or do I need to buy it ahead of time?

Buy it in advance to get the 61 CHF price. The day pass is more and more expensive closer to the date (up to 110 CHF). I'd buy it right now as you know that you'll travel that day. :)

- sbb.ch or SBB app

It doesn't tie you to a specific connection anyway. You basically have unlimited travel on all Swiss trains, buses, boats, cable cars, trams... for the day. No reservations needed at any point