Using input_boolean in automation in combination with checking for unreachable state

Hi there!

I’m trying to set up the following automation, but I can’t wrap my head around how to go about it:

  1. Around the clock, at 6, 12, 18 & 1, switch [a pre-defined zone] to a ‘default’ scene.
  2. If light(s) is changed manually, override the above, for those light(s).
  3. If light(s) is turned off (dumb switch/unreachable), return to default scene.

Step 1 is simple enough, but to accomplish want - I feel like I need a input_boolean to keep track of whether a scene is default or not. Below is what I got so far, but I’m lost as to how to do the rest or maybe there’s an entirely different method of doing what I want?

- id: ''

  alias: Default scene handler

  description: Changes the scene depending on the time of day and checks for the default scene
    trigger:
    - platform: time
      at: '18:00:00'

#Below should be the input_boolean?
   id: isDefault
# And some condition to check Whether isDefault is true or not?
  condition: []
#ie similar to...?
#- condition: state
#entity_id: input_boolean.isDefault
#state: "always(?)"
# [don't turn lights on if off]
  action:

#if True, change the scene? (For now I'm just toggling the light for easier testing)
 - type: toggle
   device_id: 
   entity_id: light.office_4
   domain: light
  mode: single

#Nice to have: 2 second fade on from off state, 5 seecond fade when changing (default) scenes

Thank you for your time to time and help if you can <3