They eat layer pellets and chicken scratch, although they like vegetable leftovers. The rooster can start to crow anywhere from six weeks to 6 months, but brown leghorns mature very early
As you see here
I always advise going to the public library and picking up a book or two. If not there try the local bookstore. Get yourself a subscription to Back Yard Poultry magazine it will be the best $15 you ever spent. At the risk of sounding harsh the time to get the answers to your questions is before you get chicks. They grow fast and there isn't much time to figure it out.
1. Chick starter on an as they want it basis, til 5-6 mos.
2. greens but not til they are older , spinach , lettuce, bits of bread. Maybe after a month or so. Start w/ chick grit and work you way up from there.
3. when he feels like it.
4. some breeds make better "pets" than others. My opinion is that none of yours will. Leghorns are layers it's what they were bred for. The same w/ RIR's but there are exceptions to the rule so don't be discouraged. Give them lots of attention, hold them alot. Feed them bits' of food by hand. Talk to them, sing to them, keep them in the same room w/ you.