Is it permissible for my daughter to return to her husband who divorced her with a single pronouncement after two years of their marriage, especially since he did not reconcile with her during the waiting period (iddah), and her child is still with him? Does she have a right to the deferred dowry (mu'akhkhar as-sadaq) and the gold jewelry (shabka) that she has not yet received?

If your daughter is content to return to her husband, then there is no impediment to that, and there are no special conditions for the return (raj'a) other than the conditions and pillars of marriage. You must know that preventing your daughter from returning to her husband if she desires to do so is not permissible شرعًا (Islamically), due to the Almighty's saying: "And when you divorce women and they have fulfilled their term, do not prevent them from remarrying their [former] husbands if they agree among themselves in a lawful manner." As for the deferred dowry (mu'akhkhar sadaq) and gold, your daughter has all her rights unless she willingly relinquishes them.