Here is the full list of all 22 Devolverland Expo achievements. It takes around 1-2 hours to unlock all of the achievements on Windows.
Collect all the hidden pieces for the third unannounced game
Watch the Serious Sam 4 trailer
Watch the Olija trailer
Watch the Blightbound trailer
Collect all the hidden pieces for the first unannounced game
Don't get caught by those frickin' laser beams
Watch the Weird West trailer
Watch the Carrion trailer
Defeat the Boss
Dare to don the Glove of Power (mkII)
Watch the Shadow Warrior 3 trailer
Watch all the trailers!
Check out all the Devolver game booths
Watch the Fall Guys trailer
Knock over all the walking Fall Guys
Collect all the hidden pieces for the second unannounced game
Break the code to the ventilation system
Pick up an access pass for the expo
Unlock the door up to Security
Take out a security drone
Pick up your essential T-shirt launcher
Rewire the electrics to get in