Huzzah for big sister asking questions.
They eat birds (or the equivalent of birds, maybe flying fish or something), and smaller flying nautilus.
I dunno, they're hard but light. Like airplanes. Only... not aerodynamic.
...uh... I'll get back to you on that one.
The same way normal ones do?
I think humans might harvest the shells for something, or use them for food, or both; like ancient people with woolly mammoths.
Other nautilus, maybe there are flying turtles or giant gryphons or dragons that eat them. I like the dragon idea... So there are turtle dragons with hard beaks that eat the nautilus.
There might be. There seems to be an abundance of flying sea life in whatever story they appear in.
....Big? I'm not quite sure. Bigger than a horse.
Yes.
They don't attack humans unless they're attacked, I don't think, but they might accidentally destroy buildings or aircraft/stuff with their tentacles when trying to catch food or with their shell when flying around.
Absolutely. XD XD XD