The wearing of the belt by sir gawain is the protagonist's attempt to symbolize to the world his

teenagers are certainly stereotyped as moody.

most people view teenagers as naturally moody and grumpy, even when this is wrong. many teens are suffering from depression but it is brushed off as "just a phase" or "that's just cause they're a teenager"

well stockyards mean a large yard containing pens and sheds, typically adjacent to a slaughterhouse, in which livestock is kept and sorted. and i'm assuming that by party you   mean a large group of people which does make sense because chicago is a very crowded place much like new york. stockyards tend to take up a lot of room due to needing the area for pens to keep animals in and the fact that stockyards are usually right by slaughterhouse where they process and distribute the product. so its much like a zoo but with some dead animal products close by.