There is a different between virgin and non virgin my friends. Their aura is different. Their spirit is different and their life also different. Only a wise person knows what this virgin is all about, why it is important and why it is so special. Yeah it has connecting with spirituality and nature itself. Yeah lots people don't know this and what they think it was only a slice of meat. But for some group this slice of meat it is likes a very precious crown and it is so precious. But they don't know why. The secret is remains a secret. :)
They say sacrifice the blood of a virgin because a virgin is deemed to be spiritually "pure". Physiologically virgins aren't much different than sexually active females, other than maybe some muscle density differences in the vaginal wall.
No. Quite often it's impossible to tell a virgin from a non-virgin unless (1) the person in question has been or is currently pregnant, or (2) the sex had just occurred within one to two days. That's specifically for women, for men it's pretty much impossible unless they have an STD (even then it depends as quite often it's possible to contract STDs without actually having sex). Also, some people define virginity differently, like some define it as any sexual experience while others define it as specifically penis-vagina sex.