swiss pass
 

1. i want to buy a 6 day 2nd class swiss pass and if at a later date can i upgrade it to 1st class swiss pass
2. By mistake I have made 2 seat reservations on glacier express for the same date. Can i get a refund for one

May be you will have a look at https://tickets.rhb.ch/en/pages/refund

It's sometimes better to pay a upgrade to first class just for certain legs of for certain days. It can be done at train stations, ticket machines or even in the train (IC and IR trains only, however).
Some local mountain trains have 2nd class only
https://www.sbb.ch/en/travelcards-an...s-upgrade.html