Updating is not supported by data source unless
The "Moto Pure" section says "La version Moto Pure de Moto G recibe actualización a las versiones del sistema operativo Android N y O..." You don't need to know how to read Spanish to see that Android O was clearly promised here as well.
In-memory Realms create several files in a temporary directory for coordinating things like cross-process notifications.
The original reply from Motorola India has since been deleted, but the damage was already done - customers are mad.
And they should be; even if O hadn't been promised, the G4 is well under two years old (the traditional major update cutoff). Most notably, the Moto X (2013) got 4.4 Kit Kat before the Nexus 4, and the Moto X (2014) got 5.0 Lollipop before the Nexus 5.
In practice, your application works with any kind of Realm the same way, although opening a synchronized Realm requires a user that’s been authenticated to the Object Server and that’s authorized to open that Realm.
While your application continues working with a synchronized Realm, the data in that Realm might be updated by any device with write access to that Realm.