You should wait until your chickens reach 3-4 months of age before allowing them to enjoy kitchen scraps.
You don’t want to give them chocolate, anything too salty, or green potato skins.
The bugs, rodents, and worms that chickens will eat while free ranging are in effect raw meat. So yes, chickens can eat raw meat.
Yes, chickens can eat bread scraps. Now for the same reason that they say not to feed bread to ducks, chickens aren’t getting anything nutrient-wise from bread. You don’t want to make it their meal.