13 day light period and on 14th day just brown during anovulatory period is that normal?

Probably: If you were 20, I would say this is somewhat abnormal, though it still could be caused by a number of common medications including birth control. However, a 13 year old woman is still establishing menstrual regularity, and it is not at all abnormal to have somewhat irregular / dysfunctional bleeding. If its bothering you I suggest you see your doctor and and discuss options

Yes: Anovulatory cycles are irregular. They can be infrequent, prolonged, light, heavy, or more frequent.