Don't feel bad, you didn't know. Sometimes chicks get mixed up, so many look so similar at a day old. What matters is that you wanted to learn in case there was a next time
Yes, they have to be butchered around 8 weeks. They just eat so much and grow so fast they're unable to stay alive. With an *extremely* restricted diet some people keep them alive for about a year at most, but it's not easy or in my opinion, fair to the bird