Achievements are important unlockables in the game IMSCARED that are needed to get the ending of the game's Workshop Edition. There are 12 achievements in total, though you only need 11 achievements to get the ending.
The First Key
The First Key can be obtained by picking up the first key under the table in the Begin level.
Master Tag can be obtained by marking all of the arrows on the floor of the Car Park.
Not To See
Not To See can be obtained by simply standing in the Not To See area, the area between the fake ending and the House, for a few minutes. This area has a ~50% chance of occurring so if you don't get it the first time you'll have to go through the game again (without resetting).
Heaven's Door can be obtained in the House, after entering the room marked "2".
The room (and the rest of the house) should turn into flesh like in the room where you get the heart in the Begin level. Before entering the next door, go to the left of the curved line of blood on the floor. Try interacting with the wall until you get the achievement "Heaven's Door."
Obtained by getting the first fake ending. After going through the Street level and unlocking the gate, you will be taken to the basement of the Begin level. After going up the ladder and going through the door, the achievement "Game Ended" will be unlocked and a popup will appear telling you to quit the game.
Same as the Peek-A-Boo achievement, however, this time you need to look through the hole in the wall after the HER Garden Maze. This time around, HER Grave will be visible by peeking in the hole.
In the Parlor you need while you get chased by HER to close the game while standing on the carpet in the Green Room.
Thanks For Staying
In the Labyrinth you need to go in to the second secret path and Click E at the Hanging Body on the left and wait some Seconds, you should get the achievement and be free to continue forward.
When at the Metro section of the game, change the time of your computer to match the "home" and "work" times written on the wall. Each of those should give you a ticket and with both of those you get the achievement.
Obtained by killing HER. The player receives this after opening the final locked door in HER's parlor.
Get The Secret End