Here is the full list of all 35 Mushroom 11 achievements.
Beat Chapter 1 Boss
Beat Chapter 2 Boss
Beat Chapter 3 Boss
Beat Chapter 4 Boss
Beat Chapter 5 Boss
Beat Chapter 6 Boss
Beat Chapter 7 Boss
Chapter 1 Strand Discovered
Chapter 2 Strand Discovered
Chapter 3 Strand Discovered
Chapter 4 Strand Discovered
Chapter 5 Strand Discovered
Chapter 6 Strand Discovered
Chapter 7 Strand Discovered
100% Cleared in Chapter 1
100% Cleared in Chapter 2
100% Cleared in Chapter 3
100% Cleared in Chapter 4
100% Cleared in Chapter 5
100% Cleared in Chapter 6
100% Cleared in Chapter 7
Complete Chapter 1 In a Single No Death Run
Complete Chapter 2 In a Single No Death Run
Complete Chapter 3 In a Single No Death Run
Complete Chapter 4 In a Single No Death Run
Complete Chapter 5 In a Single No Death Run
Complete Chapter 6 In a Single No Death Run
Complete Chapter 7 In a Single No Death Run
Finish Any Chapter Without Killing Boss
The Journey is Complete
Made it through the Eternal Ring of Fire
A Complete No Death Mine-Cart Run
Nowhere To Go From Here.
Rise Up and You Shall Reach The Top
Extreme Rocket Maneuver Skills