Is what Sheikh Ibn Uthaymeen mentioned concerning the prostration of forgetfulness the most likely correct opinion, and what should be done by congregants who stand up to complete the prayer before the imam prostrates for forgetfulness after the tasleem, and what should be done by one who doubts the first tashahhud and then becomes inclined to believe they performed it or not, and what is the extent of thecribing the repetition of the final tashahhud after the prostration of forgetfulness, and is it to be repeated in both cases?

What Sheikh Ibn Uthaymeen favored in this matter is the preponderant opinion. If actions whose place is before the salutation and actions whose place is after it coincide, then those before the salutation take precedence. However, if the worshiper doubts whether he performed the middle tashahhud and nothing becomes clear to him, then he should cast aside the doubt and perform it if it's not too late to rectify it, and prostrate before the tasleem. This is based on what Muslim narrated from Abu Sa'eed Al-Khudri that the Messenger of Allah, peace and blessings be upon him, said: "If any one of you doubts in his prayer and does not know whether he has prayed three or four (rak'ahs), he should cast aside the doubt and base his prayer on what he is certain of, then prostrate twice before he salutes. If he has prayed five (rak'ahs), they will make his prayer even, and if he has completed four (rak'ahs), they will be a humiliation for Satan."

If it becomes clear to him that he did perform it, he should prostrate after the tasleem because he built his action on his predominant assumption. This is based on what Al-Bukhari and others narrated from Abdullah: The Prophet, peace and blessings be upon him, prayed. And if any of you doubts in his prayer, let him seek what is correct, complete his prayer based on it, then salute, then prostrate twice.

If it becomes clear to him that he did not perform it and its time has passed, then he should prostrate before the tasleem. This is based on what is in the Two Sahihs from Abdullah bin Buhaynah who said: The Messenger of Allah, peace and blessings be upon him, prayed two rak'ahs of some prayers for us, then stood up and did not sit. The people stood with him. When he finished his prayer and we were expecting him to give the tasleem, he said "Allahu Akbar" and prostrated twice while sitting before the tasleem, then he gave the tasleem.

As for the tashahhud after the prostration of forgetfulness, whether it was before or after it, the preponderant opinion is that one does not perform tashahhud at all. If a latecomer (to the prayer) stands to make up what he missed after his Imam's tasleem, and the Imam prostrates (for forgetfulness), there is a detailed explanation. His ruling is like that of one who stands up from the first tashahhud: if his Imam prostrated before he (the latecomer) stood upright, he must return (to sitting). If he stood upright and had not yet started reciting, he should not return. If he returned, it is permissible. If he had started reciting, he should not return.