Top, drivers side is fog. (There isn't one on the passenger side). Bottom is combined rear and brake light bulb. (P21/5 w iirc). Assuming your brake light is actually working, then it's worth cleaning the contacts.
The top red lens has nothing in it.
The white lens in the middle is the reversing light. It has a bulb.
The bottom red lens is the combined tail and brake lights. It has one bulb. That bulb is a combination of brake and rear light.
i've replaced both of my rear light boards as the seal on them has failed over the years and let water in and corroded the contacts. one or 2 bulbs were working intermittanyly but i dont get any warnings on the dash. with the new boards and all water drained (got a good cup full!) it's all good