The largest organ in the body is the skin. That one's easy. The freezing temperature of water is a fuzzy target, depending upon how you cool it. I assume the water sample is pure, distilled water. The water usually freezes somewhat below the usual 0 C number because of supercooling. Likewise, it boils somewhat above 100 C because of superheating. The Celsius scale is not calibrated by freezing water, but rather the triple point.
That bit about hot boiled water freezing before room temp water, has been making the rounds for years. You can probably google it and finds more hits than you care to chase down. I did do such a search a couple of years ago and found a lot of "scientists" who claim to have done "scientific" experiments to prove it is true. However, I never saw the kind of data I need to persuade me. To wit: Details about the water chemistry, its preparation, the experimental apparatus, the procedure, and not even a data set of the water temperatures during the experiment. Just a claim that the boiled, "hot" water froze first. I don't even know what their definition of "frozen" was. An ice skin? Frozen solid? <0 C?
Anyway, I lost interest since I cannot support or refute a claim that is not backed up by a REPEATABLE experiment.