Error regarding demo version

Like every day I wanted to play Minecraft. I started the game, waited until the launcher was updated and a window appeared in which I was to turn on. I don't remember my old password, so I created a new one, entered an e-mail and it appeared to me that a regular launcher, instead of the "play" button, was the "play demo" button. I can't understand the error, so I decided to write this. I want to play Minecraft, but I don't want to do an operation that will remove my worlds either.