QTest Backup Restore and upgrade wizard interoperability after failed upgrade

The goal is to determine whether QTest can recover from a failed upgrade using Backup and Restore without requiring manual version alignment, and whether the upgrade wizard handles rollback automatically.

Documentation states that restore must run on a version-matched QTest instance, but it does not state whether backups remain compatible across major version jumps. Release notes describe an upgrade wizard yet omit whether it triggers automatic rollback or leaves restoration to the administrator. This leaves backup integrity and version assumptions unresolved before an upgrade is attempted.

Does QTest automatically roll back to the previous version after a failed upgrade, or is manual restoration required? Can a backup created on QTest version N be restored on version N+1 or a later major release? Is backup integrity verification required before relying on it for upgrade recovery?