They shouldn't be eating any treats harder than hard boiled egg without grit. The chick crumbles are small enough to digest without it. Sorry about your chick though.
Mine have both sides clipped and the lighter ameraucanas can get a good 3.5 feet of air. However, that works fine for me because it keeps them in the 4 ft fence while still allowing them some flying ability just in case. So it really depends on your circumstances.
It's probably a combination of saying- What's happening? It's bedtime! and Who's there?
I don't know if they develop an 'I love you' bond like humans and dogs do, but my small flock does recognize when I come outside- they all make loud 'feed me!' noises :) When I go into the run, they will...
Also, she may be skinnier because she is low in the pecking order. Try providing more spaces for her to eat without being bullied to improve her condition.
It's fine :) . Do you know if she has had it her whole life, or what breed her parents are? Some breeds have black combs, but from this picture I can't see any sign of something being wrong. A closer picture might help, but if she has had it her whole life it is probably just from one of her...
Relating this to chickens:
The crest on a polish chicken is a dominant gene, so if you breed a polish chicken to a non-crested breed, the chick would very likely have a crest. This is my understanding of it, at least. There are traits where they will both show up in the offspring as a kind of...
...a priest, Gregor Mendel, who was working in his garden when he realized that purebred tall pea plants and purebred short pea plants always had tall *offspring (Tall being dominant) *We will call them 1st generation. He then realized that about 25% of the 2nd gen was short. This is because...