Hi, my family got 4 rainbow lorikeets! need help?

And i was wondering how i can tell who is a boy or a girl? one bird has a red chest and the rest are normal red a yellow, next question is that all 3 are quiet but the red yellow one is CRAZY it doesn't shut up, how am i going to get them used to us? and not be affaird when we come near the cage, the guy said they are 4months old, is 4months to old??..hopefully they're not siblings case we want to see some babies as well.
its a big cage with a bird house in it with 2 bell balls 2 food bowls and 2 water bowls