Re: is "need to not" grammatically correct?
Think of "not touch" as the opposite of "touch."
You need to step here to open the secret compartment. -- Must do it.
You need to NOT step here or the trap will spring and you will be caught. -- Must not do it.
You must not touch any of those. is certainly more clear and direct.
Don't touch any of those! is more direct yet.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.