If a level is not loaded, it won’t be executing anything as far as I know.
In this case, you are probably going to want a blueprint that is always running in game mode/game instance which simulates what is happening in these other levels. The level of detail you need is really going to drive how you work this out, but it shouldn’t be too hard to do.
This is a very good example on if the tree fell in the woods and nobody was around to see it, does it make a sound?
In reality, yes. It does make a sound. It did indeed fall. But that’s in the real world.
In the game world, the answer is likely no. It doesn’t make a sound, it didn’t even fall. It’s all because the tree did not exist in the first place, nobody was around so the area was not loaded. It won’t exist until its area is loaded. When the area loads up, the tree has already fallen. It still doesn’t make a sound, because it had been told to fall before it was even created.
You probably want to use sub levels and stream in/out the bits you don’t need at any given time with the world browser. Then your main level can run all the calculations for the sub-levels as needed.