Here is the full list of all 54 Undercover - there are Secret Management achievements.
Purchase all upgrades at Vera's Workspace
Complete levels with 1 star.
Complete levels with 3 stars.
Find all of the notebooks
Get the 'Quick Service' bonus.
Get the 'Full Order' bonus.
Get the 'All Clean' bonus.
Check out guests with at least 5 hearts.
Play minigames at Smokin' Wheels.
Serve beers to guests.
Complete all Smokin' Wheels levels.
Play minigames at Inferno.
Serve the bowl with chocolate to guests.
Complete all levels at Inferno.
Play minigames in the Newsroom Daily.
Use the copier.
Complete all levels in the Newsroom Daily.
Play minigames at the Palace Hotel.
Serve coffee.
Complete all Palace Hotel levels.
Play minigames at the Rooftop.
Restock ice.
Complete all levels at the Rooftop.
Watch all in-game cutscenes.
Complete all levels.
Collect all diamonds.