I've moved this thread to VX Ace Support (Tutorials is for people to post tutorials, not to ask for help on how to do something).. Please be sure to post your threads in the correct forum next time. Thank you.
I'm going to call them LEVERS, because using the term SWITCH for the visual things you've got on the map and the engine's internal switches that are true/false/on/off (the logic ones) is just going to confuse things.
Do you want the levers to turn off again if the wrong ones are turned on? Or should the player just have to keep trying different combinations until they get the right one?
If they have the correct three turned on but they also have one or more INcorrect ones on, should the door remain closed?
If you don't want them to reset automatically when a wrong lever is turned, and you don't want the door to open unless they have the correct three, and ONLY the correct three turned, here's what you need to do:
Allocate a different game switch for each lever. Each event will have 2 pages - the lever in its 'off' position, with no conditions, and a Control Switches command to turn that lever's switch on; and a second page with the lever in its 'on' position, with that lever's switch as a condition, and a Control Switches command to turn that lever's switch off again.
On each page, after the Control Switches command, add a Call Common Event command. Every event, on both pages, will call the SAME common event.
Now set up your common event (do not set it to parallel or autorun). For my example, I'll say switches 1-6 refer to levers 1-6, and the door will be opened ONLY if switches 1-3 are on, and 4-6 are off (so the conditional branches are checking for the OPPOSITE result - saying if 1-3 are off or 4-6 are on, we're going to stop checking because the correct levers aren't turned on):
Conditional Branch: Switch [0001: Lever 1] is OFF Exit Event ProcessingBranch EndConditional Branch: Switch [0002: Lever 2] is OFF Exit Event ProcessingBranch EndConditional Branch: Switch [0003: Lever 3] is OFF Exit Event ProcessingBranch EndConditional Branch: Switch [0004: Lever 4] is ON Exit Event ProcessingBranch EndConditional Branch: Switch [0005: Lever 5] is ON Exit Event ProcessingBranch EndConditional Branch: Switch [0006: Lever 6] is ON Exit Event ProcessingBranch End... if the event hasn't been exited by now, the correct three switches are on and the incorrect three are off, so you can do your open door stuffPart of the open door stuff might include turning on a final switch, and giving the door event and all the lever events an extra page conditioned by that switch, so they all stay in the final position. Otherwise the player can just keep changing the switches. Actually, if you do that, you might need to use Jump to Label instead of Exit Event Processing, so the door will close again.
Anyway - that'll get you pretty close. Any extras that you do will depend on what you want to happen AFTER the door has been opened the first time.