In the picture you linked where the fog light switch is, the third button, I believe should be TRAC off for 2WD 4Rs.
The buttons from left to right on the left side are: AC 110v, center diff lock, (I think) TRAC off button for 2WD, and roll sensing curtain airbag cut off switch.
The factory AC outlet (2 prong only, no ground) is in the center console storage under the armrest. It's mounted on the front wall.
Toyota like other manufacturers, typically use a single wiring harness with many plugs, and when an option is present the plugs are used. If the option isn't there, there's a free plug. What you've found is the same on my Mazda, because I don't have the cold weather package and the rear heater button is blanked out on the dash. Some times Toyota may leave off the ending segment from the junction, i.e. like foglights on other models, the wiring from the fender area to the foglights in the bottom of the bumper is needed.
