Do chickens eat there own or others eggs.
Once a hen lays an egg, she does not know it is hers. She'll treat it the same as a golf ball or a turkey egg.
and how soon after hatching eggs do hen lay again?
It varies, sometimes quite a bit. I've had a hen that started laying 2-1/2 weeks after she hatched. She was already laying before she weaned her chicks at 3 weeks. Those chicks did not know what to do when she was on the nest. When I first saw them roaming around I thought something had gotten the hen. But no, she was on the nest laying.
I've also had a hen molt in late summer while she was raising her chicks. She weaned them at 9 weeks but she had to finish her molt before she started laying again. The good thing about that was that she had finished her molt and was back laying before the others even started their molt.
More normal is a week or two after they wean their chicks. But as you can see, they are not consistent.