I was 1.0 non-legacy, played in beta 3 and 4, and last night I was able to log in through the client and it remembered my beta character (I had long since deleted my 1.0 character). Mog Station shows me 2 FFXIV service accounts, 1 seems to be a remnant of my 1.0 account, and 2 has my beta character attached plus the ARR CE (which I didn't buy separately, I had CE back at the original release) and 15 days free playtime. I've not yet added a subscription through the Account Management page but am able to play.

My husband should have been in the exact same boat but his beta character was attached to the wrong service account, with his ARR CE plus free playtime showing with no characters. He also wasn't able to log in until today. We did everything the same way and neither of us purchased any ARR codes, yet he ended up having to remake his character.

So there was some weirdness with the beta characters, but no codes to enter and no need to re-purchase the game!