Here is the full list of all 30 Agent A: A puzzle in disguise achievements. It takes around 6-8 hours to unlock all of the achievements on Windows.
Complete all conversations with Günther
Give Günther (the crazy Norwegian bird) hiccups
Investigate Ruby's phone call records
The old phone in the shoe trick eh!? Find a shoe phone
Show us your DJ skills, scratch a record for 10 seconds
Give Agent A an 'electrifying' hairdo
Give your new ally their favourite delicacy, prepared to perfection
Complete Agent A in less than 120 minutes
Collect the fish bones a second time
Deliver a surprise to Onyx and you'll have an ally for life
Release your latest catch... HINT: not Ruby though
Make a 'Boing' sound 10 times quickly
Find every spider web in Agent A
Shoot the gun range target 100 times
Complete all conversations with Trevor
Overflow the sink a second time
Look up glissando in a dictionary, you'll know what to do Agent... HINT: start from the marked key
Sabotage Ruby's submarine
Find Ruby's submarine
Broadcast warning message to Agent B
Download Ruby's mission
Uncover Ruby's mission
Sneak into Ruby's hideout
Hit the briefcase kill switch
Access the hidden pool door
Disarm the electric pool
Open a stone doorway
Disable the house alarm system
Locate Ruby La Rouge
Infiltrate Ruby's secret lair