Dynamic loading the custom map and working with sublevels

Hello.

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

Preamble:
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?