If the icon is small in the corner, it means the card is already unlocked, and clicking on it again lets you look at it. A large buy icon and a blurred background behind it mean that the card is still closed, and clicking on it will prompt you to buy it.
No, only if you used the cheat to open the entire gallery. But then you will also have the scene with the seller open. If you did not use the cheat, then maybe there was a bug, and they opened. In that case, you can send your last save and the persistent file to me in a private message on Discord, and I will manually close these cards for you.