Here is the full list of all 25 RUSH achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Complete the Solar Flare level
Complete all actual challenge levels
Complete a level with signs to spare
Complete all tutorial levels
Create an endless loop in a level using two directional signs
Create an endless loop in a level using a conveyor
Create an endless loop in a level using a telewarp
Create an endless loop in an Easy level
Create an endless loop in a Medium level
Create an endless loop in a Hard level
Complete all easy levels
Complete all medium levels
Complete all hard levels
Complete all hidden levels
Make 6 collisions at the same time
Find a hidden level
Find all hidden levels
Place a sign on every square of the credits level
Find the hidden Toki Tori statue
Lead 1111 cubes to their exits
Fail a level 15 times in a row
Create a conveyor belt of 10 signs
Solve a level different from how the hint system suggests
Actually solve level garlic
Deliver all presents in the eight levels when they are touched by frost in December