A sin, or shame, or loss of virginity?
The speaker told his lover to look at the fleas in front of them and notice how little she refused to give him. He said that because the flea sucked his blood first and then her blood, now, in the flea, they are mixed together; This kind of communication cannot be called "sin, shame or loss of virginity". Fleas connect them in a way of "alas, more than we do".
2. What do you think is the recipient's?
Parents' attitude towards the poet's courtship?
The attitude of the recipient's parents is against him. (... despite parents' reluctance ...)
3. What is the real purpose of the poet?
Killing the flea "you" actually killed three.
Life?
He compared killing fleas to murder. This will be "killing three people is three sins" (l. 18), because if the flea follows its natural tendency to kill insects, he and his lover will be killed in the flea. He even claimed that killing fleas was "blasphemy". This is a term commonly used for acts against religion. If a lover denies the fact that their blood, so their life, is contained in a flea, it is similar to committing a non-religious act. This seems to be the opposite, recognizing their intimate relationship in fleas is compatible with religion. Admitting this intimate relationship is also admitting that it is allowed, which may lead to the conclusion that Donne hopes his lover will draw: she should give in to his desire, because there is nothing wrong with the intimate communication between two people.