What is the ruling on reciting the Tashahhud with the following wording: "All greetings are due to Allah, and all prayers and good deeds. Peace be upon us and upon the righteous servants of Allah. I bear witness that there is no god but Allah, He is alone without partner, and I bear witness that Muhammad is His servant and His messenger"? And is it obligatory to repeat previous prayers if this wording is unacceptable?

The Tashahhud, in the form you mentioned, is invalid due to its incompleteness and lack of authentic transmission. The minimum sufficient wording for the Tashahhud is: "All salutations (tahiyyat) are for Allah, and all prayers and good deeds. Peace be upon you, O Prophet, and the mercy of Allah and His blessings. Peace be upon us and upon the righteous servants of Allah. I bear witness that there is no god but Allah, and I bear witness that Muhammad is the Messenger of Allah," or "Muhammad is His servant and Messenger." Scholars have differed regarding the ruling on the Tashahhud. The majority of them hold that the first Tashahhud is a Sunnah, while some opine that it is obligatory. As for the last Tashahhud, it is a pillar according to the Hanbalis and Shafi'is, and the prayer of one who intentionally omits it is nullified.

Regarding the ruling on previous prayers for those who did not perform the Tashahhud, Shaykh al-Islam Ibn Taymiyyah preferred the view that re-performing them is not obligatory for someone who was unaware of its obligation. He stated that such a person only needs to correct the prayer of the current time and subsequent prayers. There is no harm in following those who say there is no need for re-performance after the act has occurred and rectification is impossible.