Here is the full list of all 18 Sonic Mania achievements. It takes around 10-12 hours to unlock all of the achievements on Windows.
Get through Stardust Speedway Zone as quickly as possible
That elusive perfect run, only a professional can achieve
Let the wind take you through
Try pushing a barrel to see how far it goes
Wreak havoc at the propaganda factory
You might have to submerge to find it
Try for a 3 chain combo!
We really like boats
Find the hidden item boxes at the end of the Zone
Have your photos taken in Studiopolis Zone
What would happen if you cross a bridge with a fire shield?
Barrel through the lava, don't let anything stop you
Achieve any ending
Spin the Star Post!
Collect gold medallions in Blue Spheres Bonus stage
Collect silver medallions in Blue Spheres Bonus stage
Collect all seven Chaos Emeralds
Gotta gacha 'em all