In change management, which record should be modified to restrict when a change can move to a specific state?

A company has a custom object, Order__c, that has a required, unique, external ID field called Order_Number__c.
Which statement should be used to perform the DML necessary to insert new records and update existing records in a List of Order__c records?

Which condition must be met to have a knowledge article display on the Knowledge Home Page in the Featured Content section?

In the baseline platform configuration, which Incident Management function is limited to users with roles of either itil_admin or admin?

Which method should be used to convert a Date to a String in the current user's locale?