99 winter / summer, as in
Winter of 1999, summer of 1999, etc.
Maybe they're prototypes of the game or something. It's undeniable the first one says something experimental version (Kinoko's Masterpiece Experimental Theatre? I don't know. That's probably not it).
And yes, KnK is the story about Ryougi Shiki.
And Talk is sort of afterstory of Tsukihime or prelude to Tsukihime 2, depending on how you want to see it as (Although I still can't confirm whether that last folder is Talk)