Is praying for the growth plates to open after they have closed considered an encroachment upon God, and would a response to such a prayer be considered a miracle or a divine favor, and should one stop praying for this need?

The Shari'ah prohibits transgression in du'a' (supplication), such as asking for what is impossible, whether legally or customarily. However, this does not mean that anything can incapacitate Allah. A Muslim should ask Allah for healing and to guide the doctors, for Allah has not sent down a disease without also sending down a cure for it. One must seek treatment and supplicate for healing, and strive to make du'a' at propitious times. Du'a' wards off affliction and benefits regarding what has descended and what has not. One should not despair of Allah's mercy and the answering of du'a'. It is recommended to drink Zamzam water over which Al-Fatiha has been recited, to give much in charity, to maintain the morning and evening adhkar (remembrances), to ask Allah for well-being ('afiyah), and to be assiduous in performing the early morning prayer and the reported supplications, such as the du'a' of Dhul-Nun and the supplications for distress. If Allah breaks a custom for a righteous servant, it is a karamah (a divine favor or miracle).