ringneck and Cockatoo issues

by Amy
(australia)

My name is Amy We recently got a 12 month old Sulfer Crested Cockatoo He will take seed from our hand and apple but anything else he will not tolerate.

I was wanting to know how to let him know that we are not here to harm him? also i was wanting to know how to go about training with him since he has never had any training and will not tolerate our hands on him, he just bites and lunges.
he is on a healthy diet of pellet, seed and fruit, veg.

also what is the signs of a healthy cockatoo, i will be taking him to a vet soon but just wanting to know for future reference

I have also got a problem with my 4 month old Indian ring neck He has this thing were he will growl at you and pin his eyes every time you try to take him out of his cage and usually nibbles your fingers, but he has drawn blood a couple of times he will not allow us to pat his back without growling and pinning his eyes. he knows how to step up but will sometimes bite u hard on the way up i just wanted to know is this just the way he is or can something be done to change him.

i have tried training him but he will not take any sort of treat for good behavior so therefore
the training does not work because he has no idea he has done something right

please get back to me asap
i am in desperate need of help, the longer i leave the cockatoo the more he will get set in his ways!
kind regards
Amy