Layouts and destroying objects

I can't seem to find in the documentation when objects are automatically destroyed from memory.

I have a game level layout "Level1", and when the level is completed or failed I call a new layout using [goto layout XXX].

Are the objects in Level1 with event sheet Level1 all destroyed, except for global?

Can someone point me to where this is in the manual?

https://www.scirra.com/manual/183/memory-usage

and maybe this, cause there are few extra informations

https://www.scirra.com/forum/request-quot-unload-from-memory-quot-action_t121551

Thanks - not sure why I could not find that.