Before changing code
Read the instructions supplied with the target release. Record the current version, review required PHP or schema changes and take a complete backup. Test the change on an isolated copy with outgoing services disabled.
The fresh installer and database/recovered-schema.sql are for an empty installation. They are not an upgrade procedure or a replacement for a database holding customer requests.
Trusted module packages
The owner can manage modules in Configuration → Plugins. That screen supports reviewed Desk plugin ZIPs and the module enable/disable actions permitted by your installation. Upload only a package intended for Desk and supplied through a trusted release process. A plugin is executable server code.
Plugin updates run their numbered database migrations. Disabling or uninstalling plugin code retains its records and uploads; database changes are not automatically reversed. A code backup created during a plugin operation does not replace a coordinated database and private-file backup.
After an update
Check local owner and limited staff sign-in, module availability, routing, customer request access, attachments and a test email. Check that private directories still return 403/404. Review logs before reopening normal traffic.
If an update fails, use its documented recovery path and the matching full backup. Avoid mixing unrelated old and new PHP files or running fresh setup to repair an existing database.