Use open palms when gesturing, when talking. Palm down when resting is ok but definitely try to use hand gestures when speaking

Totally agree. You could also rest them lightly on your arm rest and palms down is fine but try to bring them up to emphasize key points or to demonstrate - example, count the ways (with your fingers) you saved your co money

haha, definitely, if you want to completely distract your interviewer

Steepling also shows that what you are about to say is brilliant, it should be used sparingly, twice at most through 1 interview. See Kevin O’Leary in Shark Tank, he does it all the time and he is seen as arrogant.