Hi Jassim! As Panda said, welcome to Home Farm Ideas!
I will also try to answer all your questions as best I can but I am more of an organic gardener:)
1. I have three chickens. I only have three because I thought they would produce enough eggs from my household. I am also not a mean husband and so I must gradually convince my sweetheart to get more:)
2. As Panda said, you need to feed the younger ones crumble until they are about 10 weeks old. Like you've always heard "you are what you eat" so the same is true for your chickens. Cheap in, cheap out... Just something to keep in mind:)
Panda just finished writing an article on our website for growing FODDER! That will reduce the cost of feed and give your chickens and very high-quality food for cheaper!
Check out the article HERE!
3. When your chickens first start laying eggs they will put them in random places but over time they start to lay eggs in the nesting boxes. You can always put a fake egg and the nesting boxes to show the chickens this is where the eggs go.
4. Not really sure how to tell the age of every type of chicken because there are so many different ones and generally it is hard to tell. If you have questions like that always feel free to post photos and then we can give you our best guess based on Photos:)
5. When they are very little you need to handle them a lot so that they think you're their mama:) Once they get older they don't want to be handled as much but they still trust you because you handled them when they were little.
6. Panda hit that one on the head. When the sun goes down they will look for a place to roost. What I did was I took them out and put them in the coop and left them inside the coop for three days. The day I finally started opening the coop and letting them out they all recognized that was their home and went right back at night. There was no issue to be had for me:)
7. I trimmed their wings because I had two chickens in the past that were so curious and couldn't stop themselves from flying over the wall where two dogs killed my chickens. Like Panda said you can trim one side and that works very well. I personally trim both sides because it reduces their lift and they still have balance. I know some people would disagree with me on trimming both sides but experience with these chickens has taught me it works for my setting anyways:)
8. Not sure what you mean by "keeping your chickens away from heat"? I'm assuming you mean keeping them from overheating? Just make sure they are hydrated and come out and missed them with water. You can also put ice cubes and they're drinking apparatuses:)
9. At first you're going to need to shepard (watch over) your chickens till they are fully grown. When they're fully grown normally cats will not be an issue because your chickens will chase the cats down. The best way to defend against dogs is to have another dog that will protect your chickens. The only thing you can really do to protect them is to have them in a rather large fenced area and make sure you're watching over them. If their area is open to predators coming in, the predators will come.
I hope that helps and God bless you:)
Matt