Essentially yes. As long as you avoid “Dynamic Currency Conversion” and don’t withdraw more than £200 (or equivalent) over any 30 day period while abroad. (see below for more details)
I haven’t been to Greece or Norway, so I can’t comment on that. But in Germany card acceptance isn’t always so great. It’s been improving rapidly over the last 5 years, or so, but there are still shops that don’t take cards. I was in a pretty large supermarket last year which would not take MasterCard but only the local giro card. In short: You will need cash in Germany.
As for “moving to Norway for a year”: I don’t know how Monzo sees this. They have never confirmed if they are allowing non-UK residents to keep their accounts open. Best to ask them. [edit: Monzo have now confirmed that this isn’t a problem.]
Just to point out, that you won’t be able to receive payments from outside the UK (I don’t know if you’ll receive a salary or other income while in Norway), or make bank transfers internationally without 3rd parties. For this you might want to look at alternatives (Starling, N26, Monese, Transferwise Borderless come to mind).
More details on Dynamic Currency Conversion:
More details on cash withdrawals abroad: