Can I sync between devices through iCloud rather than using Ninox cloud
I think the only databases syncked with icloud are those in your 'My databases' tab of the native app.
What does "the native app" mean?
And where are the files stored in iCloud?
Sorry for my bad english, i mean Stand alone application which you also can use as cloud-version when you're logged in.
Not sure where Icloud files are stored for sync (I think they are not accessible as file) To make a backup of your database you can always store them on iCloud drive. But this is not used for sync. See also here for more information: