Is the prayer of one who caught the second rak'ah of Jumu'ah prayer, then completed it as Dhuhr due to his ignorance of the ruling, valid, or must it be repeated?

One catches the Friday prayer by catching one rak'ah of it. The one who catches it prays another rak'ah to complete it as a Friday prayer, based on the saying of the Prophet, peace and blessings be upon him: "Whoever catches one rak'ah of the Friday prayer or any other [prayer], then his prayer is complete," and "Whoever catches one rak'ah of the prayer has caught the prayer."

As for whoever catches less than a rak'ah, he completes it as a Dhuhr prayer, provided that he intended Dhuhr and its time has begun. If he did not intend Dhuhr or its time had not begun, it becomes a supererogatory prayer. Accordingly, praying three rak'ahs instead of the Friday prayer is not valid, and it must be re-offered as Dhuhr.