Boy marrying a girl without his parents consent

Q: A boy married a older girl without the consent of his parents in the presence of two male witnesses. Now if he wishes to tell his parents about it and they ask him to divorce the girl, will that be correct? Just because they against him marrying someone older and a few people in the family have spoken ill of the girl thus making his parents believe she isn't a good girl. Does he have to follow his parents and divorce the girl or should he remain married?

Male giving a ring to his married cousin

Q: If a girl is married and in a joking form if a cousin brother gives her a ring and told her that this is an engagement ring, then that girl denies is and then he said he is just kidding and the girl is sure that she is married and she doesn't take her cusion brother more than a brother, so she took this as a gift and wore it on the right hand and when he left, she removed it. Is her nikaah with her husband effected?

Oral sex

Q: I wanted to know if two partners play and had oral sex and semen was swallowed, would that render a person's 40 days prayer not accepted? I know oral sex is abhorred upon in Islam but what if it happened?