Mistakes in Qiraat

Imaam making a mistake in qiraat and remaining silent for more than three subhanallahs

Q: The imaan was reading Surah Sajdah. He got stuck repeatedly and paused for more then 3 subhanAllahs. Does salaah need to be repeated because he didn't make sijdah sahw? 

He got stuck like this before. He seems to be ignorant of the masla. 

He also stands with his legs far apart like a ghair muqalid. What should be done in this situation? How should he be corrected?

Not reciting Surah Faatihah in the third and fourth rakaat of a fardh salaah

Q:

1. If a person intentionally does not recite surah fatiha in the third or fourth rakat of a fard prayer but stands for the duration of three subhanallahs or more and then goes into ruku will that person’s prayer be valid or invalid. And if that person stands for less than the duration of three subhanallahs and then goes into ruku will that person’s prayer be valid or invalid.

2. If a person forgets to recite surah fatiha in the third or fourth rakat of a fard prayer but stands for the duration of three subhanallahs or more and then goes into ruku will that person’s prayer be valid or invalid. And if that person stands for less than the duration of three subhanallahs and then goes into ruku will that person’s prayer be valid or invalid.

Missing an aayah in salaah

Q: While reciting qiraat in salaah, I missed the third aayah of Surah Naas (Ila hinnaas). The remainder of the surah was completed.

1) Should I have made a Sajdah e Sahw?

2) If Sajdah e Sahw was necessary, but was not made, should the salaah be repeated?