https://travel.saga.co.uk/cruises/ocean/where-we-go/norway-cruises/idyllic-norway-1.aspx
This webpage shows the excursions for a May cruise that visits Skjolden. If you scroll to the bottom it’s Number 13. It says Easy, 500 yards of walking.
If it is Kefalonia, Princess offer the same tour and say “Tour Notes - Dress conservatively when visiting sacred sites. Shorts are not permitted and women's clothing must cover the shoulders.”
https://www.princess.com/ports-excursions/cephalonia-argostoli-greece-excursions/st-andrews-monastery-and-rombola-winery/
Saga no longer send booklets, here is a link to find out when excursions went on sale. I believe everyone who has an email on their booking should receive an email notification to book.
https://travel.saga.co.uk/cruises/ocean/the-saga-cruise-experience/excursion-availability.aspx
How many formal nights can I expect on my ocean
cruise?
Formal nights are traditionally a highlight of our cruises. They'll be:
One formal night for cruises from four to seven nights
Two formal nights for cruises of eight to 11 nights
Three formal nights for cruises of 12 to 21 nights
Usually on sea days, will not know until onboard. The dates will be listed in the today programme
Yes you do need to book the included excursions if you want to go on them, there are typically morning and afternoon departures to choose from however some time slots are more popular than others. Excursion booklets with details on the included and optional tours are sent approx 6-8 weeks before departure.