Here is the full list of all 58 Day of the Tentacle Remastered achievements. It takes around 3-4 hours to unlock all of the achievements on Windows.
Get all other achievements in the game
Flush 50 objects through time
Sit through the end credits
Play the whole game without skipping a cutscene
Defeat Purple Tentacle yesterday
Reach yesterday without turning the stereo off
Acquire a diamond
Return the stamp album to Weird Ed
Get Fred to sign the contract
Power Hoagie's Chron-o-John
Hoagie uses battery with Chron-o-John instead of plug
Red makes a super battery with only a little help from Hoagie
Try to sign the contract yourself with the quill pen
Talk to Washington, Jefferson, or Hancock while they're outside
Pick up 45 things that don't belong to you
Get all six novelty items
Power Laverne's Chron-o-John
Vacuum up a hamster
Win the human contest
Disqualify Harold
Get a tiny sweater
Try to wash the dirty car with the brush
Wake up Dr. Fred
Try to alter the contract with Booboo-B-Gone
Ask the IRS agents if they're related
Cook the hamster in Maniac Mansion (Don't try this at home, kids!)
Laverne tries the chattering teeth on her human during the human show
Laverne thinks about eating the cat
Deflate Oozo
Enter the human contest
Make a skunk
Try to microwave the hamster again after he's thawed out
Microwave the frozen hamster
Talk to Dead Cousin Ted with all three kids
Make vinegar
Clothe Laverne in the costume
Pick up 30 things that don't belong to you
Climb through the chimney with all three kids
Change the flag
Try to swap the textbook with the stamp album
Destroy a cherry tree
Make it rain
Create a cherry tree
Try to mix the red paint and the Booboo-B-Gone
Try to flush the hamster
Squirt five different people with disappearing ink
Pick up 15 things that don't belong to you
Play Maniac Mansion
Try to mix the disappearing ink with Booboo-B-Gone
Turn off the television
Open the safe
Try to put something metal in the microwave
Try to mix the decaf and caffeinated coffees
Get a job
Hoagie eats a Hoagie
Ring the front desk bell 100 times
Close a door
Find Fred's basement workshop