Headlights scenario
 

My driver's side low beam lamp went out on my 94 chevy C1500 stepside. The headlights on this model are high/low beams on the same horizontal plane on each side of the truck. After I installed the new bulb, (9006) I went to check the lights and noticed something peculiar. When turning on headlights,(low beam), the outer two bulbs would illuminate. When I switched to high beam, the inner two bulbs would illuminate. No outer. Shouldn't all 4 bulbs illuminate on high beam ?

Nope, the inner lights are aimed higher than the outside lights, hence giving them the name "high beam".

No.. All four will not light on high beam.
But here is a video on how to modify them
https://www.youtube.com/watch?v=La63i5owruo