I was able to use a Telenor SIM card when I visited Norway, which I believe also provides coverage in Denmark. However, I'm uncertain if it would work in the Faroe Islands as well. Some key sights and activities to consider including in the Faroe Islands are hiking the puffin cliffs on Mykines Island. In Copenhagen, walking down Strøget is a must—it's the city's main pedestrian shopping street and one of the longest in Europe, full of stores. For Oslo, hiking up to view Holmenkollen ski jump should not be missed. Additional tips that apply to all locations are to pack layers since the weather can change quickly. It's also wise to download offline maps in case there is no data access. You may also want to look into joining an overnight Northern Lights excursion if the timing aligns well with optimal viewing conditions.