Here is the full list of all 26 Don't open the doors! achievements.
Die 25 times.
Drink 200 pots of compote.
Kill 1000 bugs.
Explode the main door.
Read all the diary parts.
Break the beetlejuice cauldron.
Beat all the doors.
Find all the gold keys.
Upgrade diamond armor to max.
Kill 50 spiders.
Kill 1000 flies.
Collect bee glue.
Kill 50 bees.
Don't take any reward from Mr. Bee and pass through the hive gates.
Squash 100 chests.
Defeat the Pumpkinello.
Wear the glasses.
Defeat the Great Cactus.
Squash 2000 objects.
Carry a large amount of money.
Kill 10 enemies with a single hammer srike.
Kill 5 enemies with a single hammer srike.
Kill 20 enemies with a single hammer srike.
Find a book.
Defeat the Arik.
Bring the megabomb.