Yes he know a bit about A cause they sent Aria a message which he read cause Aria had left her phone at his place. And there is an episode where Aria says she is staying the night at Spencer's but in actual fact she is staying at Ezra's and it has been left up to the viewer to decide if they have had sex.
He does Know cause aria told him and they did have kinda like sex cause the episode of them both in letto was very cute and most likely counting as sex!!!
he thinks A is her friend because he detto 'you told your FRIENDS' and so he semi-knows about A and no they didn't because he oolny had fifteen minuets till class but Lucy Hale did an interview and she detto that Ezria were taking their relationship to the 'next levle' witch either means : A. their getting married o B. Their gonna have sex