(a) That at all stages of the interrogation the child was informed of his constitutional rights against self-incrimination and understood them; and
(b) That no physical force or coercion, promises, threats, or other unlawful means of inducement were employed in obtaining the confession, admission or other incriminating statement; and
(c) That a parent or guardian who does not have an adverse position, a friendly adult, or the child's attorney was present at the interrogation when a statement was given.