Is it permissible for a son to make up prayers missed by his deceased mother during her illness in the hospital, and does the reward for the prayer reach the deceased, and what should the son do?

If the aforementioned woman was unconscious during her stay in the hospital, then prayer is not obligatory for her, as responsibility is lifted from her. However, if she was conscious, then prayer is obligatory for her according to her ability. If she passed away and had missed prayers, it is not prescribed to make them up on her behalf. As for dedicating the reward of prayer to the deceased, there is a detailed explanation regarding it. It is commendable for a person to do good deeds for their parents after their passing, and they will receive a great reward for that.