(a) the validity of the purported custodian's designation;
(b) the propriety of, or the authority under this part for, any act of the purported custodian;
(c) the validity or propriety under this part of any instrument or instructions executed or given either by the person purporting to make a transfer or by the purported custodian; or
(d) the propriety of the application of any property of the minor delivered to the purported custodian.