Brain Snacks: Tasty Tidbits of Knowledge
There are more than just the four (4) Four tales and scenes from Four. In 2012, Veronica Roth wrote another scene from Divergent from Four's perspective: the knife-throwing scene. She calls it "Free Four" and she means it. It's free to read on her website. (Source)
Just like Stephanie Meyer constantly being asked to write Twilight from Edward's perspective, Veronica Roth was constantly asked to write Divergent from Four's. (She considered writing it from Edward's perspective, but her Edward is too dull to hold a chapter by himself.) (Source)
It's not fanfiction if the author writes it, but it is fanfiction if other people write stories from Four's perspective. A few dozen people have done just that on fanfiction.net. (Source)