What all stuff do I get for free in international flights?

I have my first international flight, with layover in Guangzhou and a stop-over in Wuhan, both in China. The destination is SF. I want to know what all things (other than the meals written on my tickets) are free of cost. Like food, drinks, alcohol etc. Also, what do I do if I get more hungry or something?

I am 19 (traveling alone) and would also love to know about alcohol in Chinese airlines. It's been a dream for me for a while to drink in a flight. My airline is China Southern and Economy seat. How do I ask for alcoholic drink and what all do they offer me? How do I ask for more? Is there a limit? Can they refuse? I have read somewhere there is no enforced alcohol age limit in China, but I want to be sure.

Thanks a ton!

Edit- also, what all is there to watch in in-flight entertainment? I currently have last 2 seasons of Lost unwatched and waiting to watch them on my flight.