You can think of it like a Git hash. If there was a rollback, the hash won’t be in the audit log (commit history in Git terms).

the hash is cryptographically signed by the server. So whatever state the database is, there must be a proof from the signed state up to the current one. Otherwise, the client application should handle this situation with care, as the database may be compromised.

Those signatures don’t prevent or expose or otherwise impede server-side rollbacks. They are thus immaterial to the question raised.

is out of the scope of immudb to prevent rollbacks if someone gain access to the filesystem. But even if that happen, immudb sdks will detect such situation when requesting a proof