“1. Is it safe to spray liquid nitrogen all over your house?”
Liquid nitrogen is dangerous to handle. For example, you could splash some in your eyes.
“9. Can you eat the contents of the frozen pack of peas that you just used on a fresh bruise to reduce its swelling for the past hour?”
Same question, but how about if the peas have been in your freezer for three years and used on bruises a hundred times?