No there is no way to tell visually if a woman is a virgin or not. The hymen can be broken in other ways other than sexual intercourse. If a girl uses tampons for her period, or is very active in sports the hymen can also be broken.
Even an exam can't tell if the female is virgin. There are ways the hymen can break without sex. Rigorous exercise, gymnastics, riding horses and other sports can unintentionally cause the hymen to rupture.
No. Not unless you do an internal examination...the hymen is farther in and you can't just look at the outside of a vagina and see whether it's intact or not.