Some questions about snakes:

1) Snakes' hearing is a lot more powerful than a human's, correct? Going by some articles it seems they hear picking up vibrations from the ground, with their actual ears being internal organs. Does this mean that a snake when upright (in some kind of defensive/threat pose) will have less ability to hear?
2) Some types of snakes seem to have the ability to pick up the heat emanating from other creatures nearby, a kind of body heat-sensor. Are vipers one such snake? (mostly thinking of common mountain vipers).
3) The location of the heat-sensing organs is between each eye and corresponding nostril. But does the snake actually feel heat emanating, or is this more like some kind of infrared sight? (I suppose the former?)

Much obliged to any Hercules who can bury at least one of the heads of this Lernaea Hydra ^_^