What is the ruling on supplicating between the final Tashahhud and the Taslim, and what is the ruling on one who interrupted the remembrance, thinking that it invalidates the prayer, and then performed the Taslim?

The preponderant opinion is that it is recommended to supplicate after the last Tashahhud and before the Tasleem for any good, be it of this world or the Hereafter. It is best to begin the supplication by seeking refuge from the punishment of Hell, the punishment of the grave, the trials of life and death, and the evil of the Antichrist (Al-Masih Ad-Dajjal). The prayer is not invalidated if the worshiper stops a prescribed remembrance, even if it is not in its designated place.