I know that there are different negative forms of the indicative form. Wakaran is more informal than wakaranai, and wakaranu is even more informal (and rarely used in my experience). Wakaranee is one that I have not heard of, so I am not sure of what it is.
分からない
分からん
分からぬ
分からず (Normally followed by ni)
An example of the zu ending (I think, as I rarely use it so it may be wrong :S) is:
漢字を分からずに日本語が読まれません。
「Kanji wo wakarazu ni, nihongo ga yomaremasen.」
"Because I do not understand Kanji, I cannot read Japanese."
Tanoshikatta is the past of the adjective tanoshii. The past negative being Tanoshinakatta.
楽しかった = Tanoshikatta = was fun
楽しくなかった = Tanoshikunakatta = was not fun (Thanks to jotu for correcting me there)
If anyone noticed a mistake, please correct me >_<
I hope that helped you a bit more