check the brake light relay under the hood
I found this on my 1997 Silverado and found the connection from the wiring harness to the back OS the switch itself was loose, I could wigle it arouns and make the lights come back on.
Try the light bulb.
The turn signals are not fused front and/or rear. If the rear are not working you need to check for power and grounds for the lights.
Yes, They can be switched.
Yes.
I always start with the basics.......fuses. Then go to bulbs...... Look in your fuse panel and see if you have one marked tail lights......and check it. the brake, headlights and signals work off another circuit.
Check fuses.
They have problems with the door switches.
the connection between the battery and the brake lights
the circuit boards on the taillights are bad.
Brake lights and turn signals are on a separate circuit from the tail lights. Tail lights are on the same circuit with the dashboard lights. If the dashboard lights aren't working either, check the fuse. If they ARE working, check the headlight switch.
Check the flasher for the turn signals which is under the dash on the left side of the steering column . It is different from the emergency flasher.