From page 11 of the FFXIV 2.0 Beta Roadmap pdf...
"All FFXIV service account holders qualify as testers in phase 3."
So if you ever activated an account for FFXIV, you have a service account and will be in for phase 3 at the latest. As was stated above, you should still apply if you want a chance to get into an earlier phase.
"Unfortunately many game companies are learning that if they can just keep you busy, you might not realize how bored you are." - Kachi
"Pride in your character will amount to nothing more than the level of intimacy I have when I order a burger from McDonald's" - Warfox07