Here is the full list of all 25 Little Witch Academia: Chamber of Time achievements.
Collect all of the room decorations.
Watch the Jasminka Episode.
Watch the Diana Episode.
Watch the Amanda Episode.
Watch the Constanze Episode.
Watch the Sucy Episode.
Learn all of the battle spells.
Watch the Akko Episode.
Obtain the Shooting Star Replica.
Watch the Lotte Episode.
Complete the Ghost Witch and Last Nightmare.
Collect all volumes of Night Fall.
Recover 18 Chariot Cards.
Complete the Time Demon and the Labyrinth.
Obtain the Pollux Key and traverse the Labyrinth of Pollux.
Obtain the journalism club microphone.
Complete the Hourglass of Fire and Ice.
Obtain the Gienah Key and traverse the Gienah Tundra.
Earn the title of Laundry King in the Laundry King Championship.
Obtain the Shaula Key and traverse the Shaula Desert.
Become the Queen of Spice in the Super-Spicy Showdown.
Obtain the Regulus Key and traverse the Regulus Mines.
Complete the Guard Dog and the Pendulum.
Obtain the Ankaa Key and traverse Mt. Ankaa.
Obtain the Mimosa Key and traverse the Mimosa Forest.