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Environment details? (see Admin panel -> Dashboard -> Information)
Priorities are tied to the email priority (see email RFCs), and are not mutable in the UI. You would have to alter the the *ticket_priority table directly in the database (or via a 3rd party SQL editor) and likely would need to edit the core files to support that changes.
As far as displaying the status on the open ticket screen that would depend on if you are talking about the User or the Agent side of the UI. If you are running a contemporary version of osTicket then you would be able to do this right in the UI in the Queues tab at **Admin panel -> Settings -> Tickets. If you are talking about the User side of the UI then you would have to edit the core files to achieve this.