I don't know anything about televisions, but electric things in general usually can't hold onto any settings without electricity.

So you should be able to undo any settings, and get back to the way it was when you first took it out of the box, by unplugging it and removing any batteries.

There's a possibility that a capacitor is used to store electricity for the settings chip, or that a flash memory chip is used to hold the settings without any power. In that case, what I suggested won't work, but it's an easy thing to try and I'd give it at least a 90 percent likelihood of working.