What is the ruling on ablution (wudu') and prayer for someone who used to wash their arm only from the elbow to the wrist, relying on washing the palm at the beginning of ablution, and what is the ruling on the prayers they performed immediately after learning this information, and without repeating the ablution?

If one washes the hands at the beginning of ablution with the intention of the Sunnah, then omits washing them up to the elbows, the ablution is incomplete, and the prayers performed with it must be made up. The number of prayers to be made up should be estimated to ensure caution in worship. However, if one washes the hands with the intention of fulfilling the fard (obligatory act), then completes washing the face, and then washes from the elbows to the forearms, the ablution is valid, and the prayer performed thereafter is valid according to the Maliki school of thought, which does not stipulate order in the ablution's organs. A Muslim must seek understanding in matters of their religion.