Most listings show a recommended age of 14+ ("Recommended for ages 14 and up"), so they’re aimed at teen and adult players.
Yes — some boxed adventures are playable as standalone products, can be slotted into an existing roleplaying campaign, or combined with companion sets for an extended adventure. Another title is described as a stand‑alone game inspired by a cooperative game formula.
Sanity is a tracked resource in some titles; investigations can stretch a character’s sanity and going “over the edge” reduces available actions and weakens abilities. Players are encouraged to manage or “ward off” insanity to remain effective.