1. The appointment will be done by the Imam through Allah’s permission. It will only be the close elite companions of the 12th Imam. It’s like the cabinet of a political leader
2. There are different opinions in this regard. It will be something that the current world is used to.
3. In addition to to having strong belief in Allah and the Ahlul bait, professions such as engineering, pilot, journalism, general business would be needed. The general advise from the scholars is that whether one does should do it with perfection.