His legal guardians. Have to initiate the process by first consulting the child's pediatrician. If the biological parents have joint legal custody, both must agree on non-urgent medical care of any kind, unless specific provisions in the divorce decree give one parent the sole right to make medical decisions. You can use the m-chat for screening online at firstsigns.Org, to present your concerns to his bio parents.
Mental health pro. Start with either a psychiatrist or clinical psychologist.
Yes. But it's not a simple blood test. You should start by taking the child to his primary care provider, who can then refer the child to a specialist for further evaluation if he or she thinks such a referral is warranted.