What are the secret entrances

Hint 1 of 8:

Upstairs hall cabinets

Hint 2 of 8:

Panels to Henri's room and Gertie's room

Hint 3 of 8:

Panels to Lillian's room and Rudy's room

Hint 4 of 8:

Downstairs hall clock and mirror

Hint 5 of 8:

Panels to billiard room and library