1. You can turn airports from domestic to international: if you click on the airport you reach the airport profile, where you can see a photo of the airport (not all) and get some more infos about it, e.g. coordinates, day of opening, time zone etc. Further down is "Airport Type" (Domestic or International). On the right you will have a button on Domestic airports where you can ask for upgrading to international. The "authorities" will give an order what you have to do (e.g. "if you commit to have at least 6 international routes within a year").
2. Adding runways: as far as I know you can only ask for extension of the runway ( or Check-Ins) but not for adding additional runways.
3. On the right side of the airport profile, wher you can hire gates, it will also be possible to built your own terminal(-s). You just have to decide how many gates it should have (max. 50 per Terminal) and if it should be Pax or Cargo. If you havbe enough money in your account you can build it. BUt it takes some time and will not be there from one day to the other.
I think it should be in all versions of the game. The extension-thing might be implemented on later versions, but I think from 042 on.
I hope you can upgrade your hub now and can add as much gates as you want.
