What is the ruling on repeating a verse from Surat Al-Fatihah in prayer for correction, and does it invalidate the prayer? And is the Basmalah before reciting Al-Fatihah obligatory or Sunnah?

It is permissible to count the verses of Al-Fatiha in prayer with the hand, and it does not invalidate it. However, it is considered makrooh (disliked) by some scholars and permissible by others. The original ruling is that it is not disliked. As for the basmalah (Bismillah al-Rahman al-Rahim) before Al-Fatiha in prayer, there is a difference of opinion among the imams regarding its ruling, oscillating between obligation, recommendation, and dislike. The preferable approach is to recite it to avoid disagreement.