2002 F150 brake/turn signal

First remove and test the brake and turn signal bulbs, if ok energise the brake and turn signal circuits, connect a voltmeter to the center of the bulb holder to shiny part of the metal body frame , should be battery voltage if ok the light frame has a bad earth,if no voltage a bad connection or broken wire going to the light.

Blown bulb. The bulbs use a two wire one wire for brake and turn signals another for tail light

Bad socket

I had a similar problem, you might want to try changing out the BWD - Relay - Multi-Use Part #R4823. It is located under the Dash, beside the Steering Column. I purchased one from Canadian Tire for $25.00

For the defroster:

Turn the defroster on and check for 12v at the connector on the window. If you have 12v, check for breaks in the element (the thin lines running across the window). If you do not have 12v and the fuse is good, the culprit will most likely either be the switch or the wiring.

For the right park light:

Check the bulb socket. You should have 12v at one terminal (with the park lights on) and ground at the other. If the voltage and ground are ok, you either have a bad bulb or possibly a bad socket. By bad socket I mean they can sometimes distort and not allow the terminals to make good enough contact.

Hope this was helpful.

check fuse if fuse is good inspect wire for breaks in it

Check the bulb. The problem has to be right there at the socket for the left rear. You do understand how the two filament bulbs work? The brake and turns use one filament, while the park lights use the smaller , less bright filament. And the bulb has two buttons on the bottom that touch two buttons in the socket. That is how the current is carried separate for the two lights.
It sounds like your bulb is wrong, or the socket itself is compromised.

You have a broken wire to the turn/brake light portion of the light as they use the same wire. Or where the plug goes into the light assy could be bad. Torsion mount lights are horrible and you should think about replacing with a universal light that you can wire direct.

no disrespect but....
Check the book and make sure you are using the proper bulbs on all sides. (3957 looks just like 3956 but wont work right)

sounds like brake shift interlock is not sensing brake pedal apply so it can activate solenoid to allow shft from park.
Check bulb socket and replace if bulb ok