Well, GCCs are mostly fruit eaters in the wild so free-feeding (putting the food in a bowl in the morning and leaving it there all day long) protein food (seeds, pellets, etc) is not recommended as it makes them go into breeding condition and damages their livers and kidneys (because they were not 'built' to process high protein). I recommend feeding cooked whole grains mixed with chopped veggies accompanied by a large portion of fruit and a smaller veggie and leafy green for breakfast and all day picking and a low protein (budgie in the winter and cockatiel in the spring and summer) seed mix for dinner.
The light schedule birds need is the solar one (think of chickens and the birds out in the trees). They need to wake up with dawn and go to sleep with dusk without the interference of artificial lights. This is because their endocrine system (the one that tells them when to produce sexual hormones and when not to) is governed by light (this is called avian photoperiodism and if you put that on your search engine, you can find lots of info on it but there is also a thread about it here: viewtopic.php?f=18&t=13220&hilit=photoperiodism
). When you keep a bird on long days all and high protein all year long, the bird's body thinks it's breeding season all the time and that's real bad for them because they not only become chronically and highly sexually aroused (regurgitating in a bird that has no mate is a symptom of this) but this also causes physical discomfort and even constant pain (their sexual organs grow during breeding season and shrink when it's over but, if it's 'on' all the time, they get to be too large and start displacing other internal organs).