I need someone who played the first FFXIV

I'm so confused because i bought a realm reborn yesterday and today i logged into my old 1.0 account on accident(I thought i tried to login with it before and it didnt work) now I'm confused as to if i had to even buy realm reborn at all.. I know its just a 3 day trial.

after the trial is up would i have to buy the full game or just set up a sub?

and does anyone know if SE would do something like an account merge or just transfering the registration code over so that i can play my old 1.0 characters that were leveled up.

Thank you for any help