Here is the full list of all 13 Alicemare achievements. It takes around 6-8 hours to unlock all of the achievements on Windows.
Look the true end
Speak to Cliff on the phone
Find the extra scene
Think of another answer to the river puzzle
Find the Cheshire Cat ending
Choose Joshua
Choose Stella
Choose Chelsy
Choose Letty
Look under the Joshua's bed
Reach level 7 in NuTetris
Eat the poisonous mushrooms
Play Stella's piano