Here is the full list of all 35 80 Days achievements. It takes around 30-35 hours to unlock all of the achievements on Windows.
Walk the ocean floor
Save an Artificer and her device from falling into the wrong hands
Completed trip in 50 days or less
Completed trip in 40 days or less
Become an American boxing champion
Travelled all the way around the world without using a bank
Completed trip in 60 days or less
Travelled across the northern wastes aboard the Floating Reservation
Completed trip in 70 days or less
Completed trip in 80 days or less
Knock out Jesse James
Bring a murderer to justice using your powers of deduction
Travelled all the way around the world
Visited at least 20 cities in a single trip
Visited the World's Fair in Paris
Travelled all the way around the world without using a hotel
Visited at least 30 cities in a single trip
Travelled over 239,000 miles in total
Find true love waiting for you on your return to London
Embark on a life of crime in the company of the world's greatest jewel thief
Reignite love in the frozen north
Betray a living being to the Didacian nuns
Descend into the heart of the earth itself
Visit the secret observatory of Mount Elbrus
Travel beneath the ocean waves with a certain infamous Captain
Ruin the life of a man of Vienna
Rescue a man from hanging
Aid the Belgrade resistance
Launch for the Moon!
File a news story in the Times
Become intimate with an airship
Enter the secret vault of the Artificers
Go over Niagara Falls!
Have Monsieur Fogg die
Spend the night in Machu Picchu