Does gazing at the 'awrah (private parts) during prayer invalidate it in the Hanbali school of thought? And what is the interpretation of Malik's saying, "Indeed, whoever gazes at the 'awrah of one praying, their prayer is invalidated"? And must prayers be repeated if the worshipper was ignorant of that? And does prostrating on the same spot once or wiping the spot before prostrating invalidate the prayer, and must I repeat it if it does invalidate it?

The Malikis hold that the relied-upon opinion is that prayer is not invalidated by looking at one's own 'awrah (private parts), or the 'awrah of the Imam, or other worshippers, whether done intentionally or unintentionally.

As for the Hanbalis, the prayer of one who sees his own 'awrah through a shirt pocket or similar means is invalidated. However, seeing the 'awrah of others does not invalidate the prayer.

Wiping the place before prostrating does not invalidate the prayer. However, the Sunnah (definition) is not to wipe more than once, except out of necessity, such as intense heat from pebbles or the presence of something that would harm the one prostrating.

As for prostrating only once in a rak'ah, this invalidates the prayer because it constitutes abandoning one of its pillars.