FaceTime is available n Norway yes.
FaceTime itself is free.
Any charge would come only from the cost of the internet connection being used. There is no extra cost from Apple to use FaceTime
If using home Wi-Fi than no extra cost beyond your Wi-Fi cost if any.
If using cellular data on an iPhone or cellular iPad, then the cost would be whatever your cellular service provider charges for your data. Do note video calls can use a lot of cellular data.
You can use either the phone number or the email address it does not change the way the call is connected as long as the phone number is associated with an Apple ID.
If the number is not associated with an Apple ID, the call will be a cellular voice call, placed through a paired iPhone if any is available. If that Happens the carrier may charge for international voice calls and minutes usage depending on your cellular service plan.