is it possible to check variable of all object instances to see if they are all true
You can check the opposite.
Assuming you check a simple yes/no var=1 or var=0
To check if all objects have var =1
If var of object = 0 / set scenevar true to 1
If var true = 0 all objects have var =1
If var true = 1 at least 1 object has var=0
I have fixed this issue