Hi, There are no rail lines in the north of Norway past Narvik. If you want to reach Porsa/Hammerfest from Alta taking the roads you mention you need to hike you bike over very dangerous terrain (Trollkuken) with unpredictable extreme weather. I would not recommend you try this, Unfortunately the E6 is the only real road to cycle on in areas of the far north. The only gravel you’ll find will lead to deadends (with the exception of the Post road).