you wont hear them chirp till they pip internally. I don't have a lot of hatching experience so someone may be able to better answer but just from experience its usualy late on the 20th or 21st day when there ready to start hatching and sometimes it takes hours from internal pip to external pip hope that helps you some
Depends on the chick. I've had some start making noise early. heck I've had one hatch on day 16 of incubation and live. Then i've had some that didn't make any noise that i heard til they hatched. Each chick has a different personality. Some are quiet and some are noisy.
Thus far, all my chicks that are bantam sized have started peeping internally on day 19 and hatched out by the evening of day 20. All of them. The only chicks I have had hatch out on day 21 or even pip externally on day 21 are the large fowl (regularly sized chickens) and those were peeping on day 20.