1. How is a whistling teapot like a volcano?

Because of the build up of pressure. There is so much steam coming from such a compressed point, it’s coming out in force.

Now think of that same spot being closed, it only has one place to go but it can’t leave, so that pressure will build and build and then BOOM, it explodes.

In short, the answer is the pressure being released from a small point, and how that energy is released.