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