the key slot i dont know but what i can answer is the key that goes for the door in the hidden lake is in puffle rescue follow the shadow and bubbles give you air and when you see a stair case you go down it and ba baam your in the seceret room
in your coin slot tied on them
you find it at the dance club
The Hidden Lake
key
You can buy a club penguin guide book. Then, look in the content for key merchandise and go to the page.
it is in the mansion
with a key!
in the library
in the hidden lake
nothing
under the lounge
noting