To trade keys, you will need two systems, each with a game, preferably each game being a different version. Next, you will need to open Unova Link and go into the Key Sharing area. You will not lose the keys, for they are merely copied over to the other game. Please bear in mind that you can only trade keys that your version gets (i.e. only a person with White 2 can give away the Easy Mode key, even if a person with Black 2 has the easy key.) Hope this helped!