1. Food is served through large public plates, and public chopsticks are basically provided for you to divide the food into your own plates. If there are public chopsticks, use them to divide the dishes. If there are no public chopsticks, or you are not sure whether there are public chopsticks, you can wait and see what others do, and then follow suit. Sometimes the warm-hearted host in China will help you divide the food on your plate, which is normal.
It is impolite not to eat what is given to you. If you are offered something you absolutely can't stand, eat the rest and leave the rest on your plate. A little food left generally means that you are full.
It is impolite for you not to eat the food allocated to your plate. If you really can't eat some food, you can eat others first, and then leave what you don't want to eat on the plate. Usually a little food left on the plate means that you are full.