With Okta Retention Policy, App generated data and reporting based on log data older than how many months is automatically removed (not considering the Backup Data)?
Solution: This data is never removed, as per GDPR

With Okta Retention Policy, App generated data and reporting based on log data older than how many months is automatically removed (not considering the Backup Data)?
Solution: 3 months

You just re-enabled IWA DSSO and notice it's not behaving as it should. What is an aspect you should keep in mind?
Solution: That when re-enabling IWA DDSO a new set of Identity Provider (IDP) routing rules have to be created

Okta has a json representation of objects such as 'users', json schema interchanged on API calls, as an example, but what about the format of information regarding of a user going to a SCIM server for creating the user in an On Premises application?
Solution: Format stays the same: json

When you are trying to federate (via WS-FED) Office 365 with Okta:
Solution: You can try to federate multiple Office 365 custom domains into a single Okta Office 365 app instance via SWA SSO protocol