I'm gonna tick off the achievements I can do on mobile, and I will continue on PC, when I get good hardware.

There are 547 achievements.

Levels From Easiest To Hardest (In My Opinion) (GD World/Subzero/Meltdown included)

The Tower
Payload
Beast Mode
Space Pirates
Machina
Years
Back On Track
Frontlines
Stereo Madness
Polargeist
The Sewers
The Challenge
Round One
The Seven Seas
The Cellar
The Secret Hollow
Ember
Monster Dance Off
Dry Out
Blast Processing
Viking Arena
Striker
Airborne Robots
Press Start
Base After Base
Jumper
Fingerdash
Nock Em'
Can't Let Go
Time Machine
XStep
Dash
Geometrical Dominator
Power Trip
Electroman Adventures
Theory Of Everything
Hexagon Force
Cycles
Clutterfunk
Electrodynamix
Theory Of Everything 2
Clubstep
Deadlocked