Jamaat Salaah and Imaamat

Imaam performs 2 rakaat of witr followed by a single rakaat

Q: The mosque I am going the imaam makes the witr as 2 rakaat followed by 1 rakaat in which he makes qunut after the ruku whereby everbody raise hands as in duaa and says everytime amin to the duaa.

If a Hanafi follows this imaam is his witr also valid? Secondly they start the tarawih rightaway after the fard of isha thus they dont perform first 2 rakaat sunnah. When should I pray this?

If someone prays at home intentionally then is it sunnah for him to repeat the same salaah after he has prayed?

Q: One person said: "as praying in congregation is a strong sunnah, and although its intentionally abandoning is makruh tahrimi , the ulama said its repeating is sunnah." Does this mean if some does pray at home intentionally then it is sunnah for him to repeat the same salaah after he has prayed?

Hanafi Imaam reciting an Aayat of Sajdah according to Imaam Shafi'ee

Q: If a hanafi Imaam recites an Aayat of sajdah (that is according to Imam shaafi'ee Rahimahullah and not according to Imam Abu Hanifah Rahimahullah e.g: The Aayat of sajdah that appears at the end of the 17th juz) in salaah, and he is followed by muqtadis of the different mazhaahib, then what should he do in this situation. If he doesn't make sajdah will their salaah be valid? Is there a solution to this?