if video contains license plate numbers and people faces?
There is no legal reasonable expectation of privacy when a person is out in public. You can post any footage from your dashcam as long as you're using it as a dashcam to record your surroundings on public roadways while you're driving your car on public roadways.
Have seen many dashcam footage uploaded by peoples. I don't think it's ilegal.
no, but if you are showing License Plates and people for profit then yes.