This depends a lot on what breed. With Silkie you can not tell until they are crowing, Welsummer you can tell at day of hatch. What breed do you have? Oh photos help to.
You can give you birds medicated feed up to the point of laying. You do not want to eat eggs from medicated feed, Depending on the breed and time of year Point of lay could be anywhere from 3 to 7 months.
Alaskan which Facebook page are talking about?