I have two grammatical questions!:

1-When do we use "each" and "each one", same question for "any".

For instance:

Each/Each one of you must tell me the truth. If any/ any one of you tries to lie to me, they'll have problems.

2-I regulary see "kids games", "kids activities". This structure looks strange to me. Indeed, "kid" in this case is like an adjective, so it shouldn't be plural, according to what I know.

Is the real structure "Kids' games", and people simply forget the '?