Dynamic loading the custom map and working with sublevels


I have a big and complex question regarding the beginning of the work of loading the map and working with sublevels.

In our project, we use random level generation. And now we use it through the use of streaming levels. I choose which Levels to load from the large pool of matching levels.
But all these levels are not added to one persist. Since there are a lot of them and they are constantly changing and being added or removed.
I load the levels using the function:
ULevelStreamingDynamic :: LoadLevelInstance (…);

Question number 1:

When I add a level using the ULevelStreamingDynamic :: LoadLevelInstance (…) function, only the persist is loaded. All sublevels that are added to this level are not loaded.
How do I get a list of sublevels that are added to the downloaded level? I can’t find them at all.

Question number 2:

It would be very convenient to find a place in the process of loading a new level and add there all levels that were chosen randomly and need to be loaded. Maybe someone knows how to do this?