If there is no other data to use, use the in-built device ID (for example, using react-native-device-info library) as an identifier. When the user authenticates, you can go through a one-time refresh where the old records are updated with the authenticated users ID.
You can find information on the
@aws_auth directive here: https://docs.aws.amazon.com/appsync/latest/devguide/security.html#aws-appsync-security — it’s not valid for generic OIDC, as far as I can tell from the documentation. However, I have not tested it.
Nope — I did the right thing. There is a blog type which has an embedded posts. So you can say “give me blog with ID and all its posts”. With a small adjustment to the schema, you could also say “give me post X and the blog it belongs to”, but that isn’t within the generated schema.
Without an in-depth look at your setup, I won’t know. I suggest you open up a question type issue on the aws-amplify/amplify-cli repository on GitHub.