Does prayer become invalid if the worshipper makes a mistake in a word of Al-Fatiha, then intentionally completes the verse, then repeats it? And does prayer become invalid if one continues reciting after making a mistake in reading one of the words?

This answer indicates that the questioner is experiencing intrusive thoughts and advises them to disregard them. Regarding prayer, if a worshipper makes a mistake in a word of Al-Fatiha, it is sufficient for them to repeat only the word they erred in and what follows it, and they are not required to repeat the entire Al-Fatiha. Intentionally reciting the entire verse or the entire Al-Fatiha after the mistake does not invalidate the prayer.