In most countries (and states of the USA), it is illegal for a 15 year old to have sex.
No it's not illegal.
It is not illegal for them to date, but is is illegal for them to have sex.
yes it's still illegal
No, it is not illegal for a 15 year old boy to date an 18 year old girl in the state of Illinois. However, it is technically illegal for them to have any sexual contact.
No that is illegal.
No.
No.
Dating is not illegal; sex is illegal.
no
yes
it isn't but it should be illegal
Dating is not illegal as long as the minors parents are OK with it. Sex is of course illegal.