Here is the full list of all 35 Disc Room achievements.
EXPLORE ALL ???? ROOMS
QUIT TO MAIN MENU WITHIN 2 SECONDS AFTER DYING
COMPLETE HARD MODE
UNCOVER THE GOLDEN MYSTERY
DEFEAT THE ULTIMATE GATEKEEPER USING EVERY ABILITY
SURVIVE 20 SECONDS IN EVERY ROOM
DIE FROM ALL DISCS
EXPLORE ALL ROOMS
DISCOVER THE FOURTH GOLDEN ROOM
SURVIVE 10 SECONDS IN EVERY HARD ROOM
EXPLORE ALL HARD ROOMS
SURVIVE 20 SECONDS IN ANY HARD ROOM
START HARD MODE
DEFEAT THE ULTIMATE GATEKEEPER
???? THE ????
FACE THE GOLDEN CARCASS
FOLLOW THE PATH
UNLOCK ALL 6 ABILITIES
DISCOVER THE THIRD GOLDEN ROOM
DEFEAT THE PHANTOM GATEKEEPER
WALK 10K STEPS
DEFEAT THE CARNIVOROUS GATEKEEPER
END A RUN FROM THE MAP
DISCOVER THE SECOND GOLDEN ROOM
SURVIVE 20 SECONDS IN EVERY ROOM IN ONE ZONE
DIE FROM ALL DISCS IN ONE ZONE
DISCOVER THE FIRST GOLDEN ROOM
SURVIVE 0 SECONDS OR LESS
HOLD DOWN FFW FOR 10 SECONDS STRAIGHT
SURVIVE 60 SECONDS IN ANY ROOM
DIE FROM 4 DIFFERENT DISCS IN ONE LIFE
FEED ???? 4 ????
DEFEAT AND REVIVE AN ANTIBODY
DEFEAT THE OVERGROWN GATEKEEPER
DEFEAT THE ARMORED GATEKEEPER