Mushroom naming is either personal preference or to align with scientific nomenclature for easier time with alchemy. But f they look the same, they function the same, unless it's a doppelganger, one of the "Hydras", or one of the Dreamshroom/Deathspore/Mindsap/Echo mushrooms.
The forest does actually have thematic storyline, it's supposed to follow 'Dark Forest' story narratives.
If you're talking about the shack then yes there is a dependable way to get one of the keys. It's referenced in one of the journal entries.
Now, Where did you encounter a need for scissors in the forest? I've been trying to identify the use for a pair of scissors for awhile now.