Here is the full list of all 22 BeatBeat achievements.
Pet the dog.
Clear all levels in the Grow folder.
Clear all levels in the Flourish folder.
Clear all levels in the Resolve folder.
Clear all levels in the Suffer folder.
Have an unreasonable number of windows open on your desktop.
Catch a FEESH.
Clear one level in the Grow disk.
Clear one level in the Flourish disk.
Clear one level in the Resolve disk.
Clear one level in the Suffer disk.
Clear any level with the Full-Auto mod equipped.
Clear Shoujo on Extreme with the AutoMover mod equipped.
Clear any level with the Big Beats mod equipped.
Clear any level with the x1.15 mod equipped.
Change the color of your totem in the Settings menu.
Start a level while your truescore modifier is greater than 1.
Lose a life.
Clear a Boss fight while using its totem.
Answer all of B9's questions.
Complete one of the game's endings.
Complete the True Ending.