Subject to subsection (b) of this section, a juvenile court shall rule on a guardianship petition: within 180 days after the petition is filed; and within 45 days after the earlier of: receipt of all of the consents required under this Part II of this subtitle; or trial on the merits. A juvenile court may not enter an order for guardianship of a child under this subtitle before the later of: 30 days after the birth of the child; expiration of the time set for revocation of consent, and not waived, under § 5–321(c) of this subtitle; or expiration of the time to respond to the show–cause order issued under § 5–316 of this subtitle.