You need a save system atleast basic one to know player progression state. level 1 2 3 , on each level progression increment you can have an event to unlock doors or simply you can ask “is it unlocked?” when player tries open.
However if design wise. You can also make it a little bit fancier after setting your save system.
You can have some keys for player inventory to that unlocks other levels as reward or drop.
When player tries open a door you can check if player has key