...
If a web experience contains widgets not present in the destination environment, the restore will fail.
If the ArcGIS version of the backed up Web Experience and the Destination Environment do not match, a warning message will be shown in the restore preprocessing stage. This is because the data structure of web experience configurations has changed between versions, which may cause a number of issues ranging from format changes to feature services not displaying.
Scene Services:
Scene services will need an underlying source package related to the item in order to back up as a hosted scene service, otherwise Backup My Org will treat it as a registered service pointing to the original file if source information cannot be saved.
For more information about Backup My Org, including supported items and system requirements, please see our product page.
...