Staff ticket and multi leg tickets

Hello, if I fly from Amsterdam to Dubai, Dubai to phuket, next use a one way ticket from phuket to Gaunghzou, and return on the previous ticket gaunghzou to Dubai, then Dubai to Barcelona. Primarily a staff ticket.

If for example there is no seats our of gaunghzou can I fly from gaunghzou to Hong Kong then fly to Dubai etc.

Thank you