Amnesia is a good room
Actually, Hackers is the easiest. My 10-year-old was very involved, and the rooms are filled with old toys.
The roulette room is the easiest, then the vault, and the carnival is the hardest
It's not really geared towards any age. It just depends on observation and investigation skills. They do range in difficulty though. I haven't done them all so I can't say which is easier
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