"Inne i" and "innenfor"
I was studying Norwegian at the library while my Swedish friend was studying as well, and I asked her what was the difference between "inne i" and "innenfor". I don't think there is a grammatical difference, but I don't understand when I am supposed to use one or the other. She tried to explain, but it's very intuitive for her, and I still don't get what the difference is. Could someone explain ? Takk !
So, they can both mean "inside", or sometimes "within", but as you've gathered they're not used interchangeably.
"Innenfor", and its antonym "utenfor", usually deal with some sort of explicit threshold, border, or limit. It's also used in relation to fields of science, research, work, etc.
"Inne i", or often just "i", is used when referring to (being on) the inside any other thing or concept.
Of course most things and concepts have their limits and borders and so on, but if that's not the first thing that comes to mind when thinking of them, then it likely doesn't count.
Here are some examples to make it clearer:
Innenfor døren/grensen/gjerdet (the door, the border/limit, the fence)
(Inne) i rommet/esken/kjøleskapet/hulen (the room, the box, the fridge, the cave)
"Innenfor" can also be used to mean "further inside" (than something) or "behind" (something).
You could also say for instance "Gjemt inne i døren" (or "inni døren", it's synonymous). Then it would mean "hidden in the door" (as in you would have to cut through it to get to it).
A little fun fact, innafor is also a common slang used to say that someone or something is great. It kinda refers to "surpassing the lower limit". So let's say a dude is handsome, he would be "innafor", or if you got a B on the test your friends might say that's "veldig innafor" :)