Here is the full list of all 24 Almost There: The Platformer achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Earn All Stars
Earn All Stars in World 3
Complete World 3 Tier 4
Complete World 2 Tier 4
Complete World 3 Tier 1
Complete World 3 Tier 2
Complete World 3 Tier 3
Earn 300 Stars
Earn 400 Stars
Earn All Stars in World 2
Complete World 2 Tier 2
Complete World 2 Tier 3
Complete World 1 Tier 4
Complete World 1 Tier 5
Complete World 2 Tier 1
Earn 200 Stars
Earn All Stars in World 1
Complete World 1 Tier 2
Complete World 1 Tier 3
Earn 100 Stars
Complete World 1 Tier 1
Earn 10 Stars
Earn 25 Stars
Earn 50 Stars