Secondly, when they feather out is typically when we put them out. In other words they aren't fluffy lil balls any longer but have their "adult" feathers in. You live in a much colder climate than me and that might change things, though.
Sexing can be difficult and takes time to notice some subtle signs, but some chickens you won't really know 100% until they crow (or not).
Good luck with your folk and you did well joining this site. There are some really good folks here.
BYC has a lot of helpful stuff in the articles section (see the tabs at the top of the page). You might want to start with this one. https://www.backyardchickens.com/articles/how-to-raise-chickens.47660/
In the store tab is "Raising Chickens for Dummies" which I presume is an excellent book or it wouldn't be there . My two most used books are "Chickens in your Backyard, A Beginner's Guide" by Gail Damerow and Rick Luttmann and "The Chicken Health Handbook" by Gail Damerow. I recommend reading them cover to cover. There will be a lot of stuff you don't need now but it will familiarize you so you recall that it is addressed and can go back to it.
As for gender, it depends on the breed as to how soon you can tell gender. Most are pretty obvious when the fluff is gone, some sooner, but some can confuse you almost until they are grown...sometimes because you are hoping so much for the bird that looks like a roo to really be and hen The bird in my avatar was named Henny. At first confusion, extended due to wishful thinking. But he was a lovely roo.