Yes and Yes, and YES!
My BR was my first layer at just under 18 weeks, 3 weeks later her sister started laying, and a week later the other one started laying. My BO started laying next, but I have 6 of them, and only 3 BR. For 6 weeks I only had 3 hens laying, in 2 1/2 months with 6 steady layers, they have laid 190 eggs since Sept. 1. But the 6 have only been laying for a month. I have been very pleased, I have 14 hens total, and 4 are still not mature yet, and the others are still getting the hang of laying. I still want to get some Marans, cause I love the chocolate color eggs.