All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
We have already issued Fataawa 86918, 84403 and 83727 clarifying how to make up many missed prayers, so please refer to them.
As regards the Fatwa which you mentioned in the question which states that a person should make up one day’s missed prayers each day, then we do not think that this Fatwa is correct. The scholars stated that this is not enough unless a person could not do more than this, as Allaah does not burden a soul more than it can bear.
Al-Hattaab from the Maaliki school of jurisprudence, said: "…If a person makes up two days (missed obligatory prayers) each day, he is not considered neglectful…as regards making up one prayer with each obligatory prayer, then -as the common people say- this does not mean anything. However, if a person could not do better, then he should not abandon this, because little is better than nothing."
It depends on one's ability, one should make up missed prayers, and whoever is able to make up two days each day, he should do so, and if one is able to do more, he should do according to his ability.
However, reciting one Tasbeeh (glorifying Allaah Saying: “Subhaana Rabbiyal-‘Atheem” when in the bowing position and: “Subhaana Rabbiyal-A’laa” when in the prostration position) in the bowing position and prostration is an obligation in every prayer as clarified in Fatwa 92193, and one should not claim that it is not an obligation to utter Tasbeeh when making up a missed prayers.
As regards the issue of not performing supererogatory prayers for whoever has missed obligatory prayers, then some scholars stated that the one who has many missed prayers may only perform obligatory prayers and not perform any supererogatory ones because the Prophet missed four prayers on the day of the battle of Khandaq, so, he ordered Bilaal to call Iqaamah and they prayed Thuhr, Asr, Maghrib and 'Ishaa’ and it was not reported that the Prophet performed a supererogatory prayer between these prayers. Therefore, it is more appropriate to perform obligatory prayers than performing supererogatory prayers, unless the missed prayers are very few, in which case, one may perform supererogatory prayers as well.
Some other scholars stated that one should not abandon the supererogatory prayers especially the Witr and the two Rak'ahs before the Fajr obligatory prayer.