Update script fails: database already upgraded
Please check related question and answer on this link: How do I deal with &quot;Your database has already been upgraded&quot; error?

Also see documentation on upgrading CiviCRM for Wordpress on the following link: https://wiki.civicrm.org/confluence/display/CRMDOC/Upgrading+CiviCRM+for+Wordpress

It is also recommended to use the CiviCRM stackExchange search to check if a similar question has already been asked before posting a new question.