Never, some cases may be the exception though: 1) after a fight 2) on your menstural cycle 3) suffer from a severe illness 4) cut yourself 5) heard a Justin beiber song (warning: may lead to severe...
A hymen is the symbol of virginity for a women. It is also a part of the vagina. If it breaks during the first time insertion of the penus bleeding is the result.
A normal bleeding time for the Ivy method is less than five minutes from the time of the stab until all bleeding from the wound stops. Some texts extend the normal range to eight minutes.
Maybe but usually not because your body takes several months to "adapt" to a regular cycle and flow. Bleeding may be very light and last a very short time. Some girls will have a more regular start...