Got a rainbow lorikeet,was wondering if u know approx age & if it is illegal to rear it and keep it my self?

i live in south australia. it has all its feathers looks old enough to be close to and adult i think. it has dark eyes and its beak is black. with a bit of yellow fading to black near its face. it aslo hasnt atempted to fly and has snuggled up to some bottle brush we put in the cage. i dont know what to feed it coz of the age thing. my stupid cat(who we are considereing gettin rid of) caught it. we have had it for 2days now and is very lively and has only drank water and eaten a little bit of strawberry. my partner has managed to pat it with no skwarking or bitting which makes me think is young. help with and age would be good to. thanks