So, how do you turn OFF Developer Options?

You got two ways of doing this.

This is how it works on HTC, with Samsungs you might have to factory reset to hide it. Well, a factory reset will work on ANY phone to hide it tho.

To simply disable it it, just open Developer Options and tap the ON/OFF button up to the right. By doing that, you disable all/any settings through Dev options.

To hide it, it’s slightly trickier but still not hard. Just go to Settings > Apps > All > Settings, where you clear Data. This might clear other things as well. In case you wonder “why did THAT go?”. But, the basic settings seems to stick. But, it hides Developer Options again. I assume it disables it as well.