Upgrade steps:
Backup installation folder and DB.
Uninstall V5
Install V5.1 app
Upgrade DB using scripts in folder "Incremental Upgrade - OnPremV5.1"
Apply new licence for V5.1
Apply web.config file changes e.g ConnectionString
In case of any DB errors during upgrade, use the scripts in folder "Rollback - OnPremV5.1" to rollback DB to V5