Method of Salaah

Q: My question is what do we recite behind the Imam in the third rakaat of Maghrib and third and fourth rakaat of esha and dhur and asr. 

Q: I recently led the jamaat for zuhr salaah and for some reason I have doubts and cannot recall if I read the same surah in the 1st and 2nd rakaat (after surah faatiha). I don't know the two gentleman that read behind me. What should I do to rectify this? What if I cannot find them?

Q: I work on a coal mine, where the roof is not high enough to allow one to stand up straight. We work morning shift for a week and night shift the next week. Dhuhr is delayed until returning to surface when working morning shift, however salaah is performed underground when working afternoon shift. As one is required to stand upright, is it required to a) sit and pray (and then repeat the parayer when on surface) or b) stand and pray (even though one stands slightly crouched)?

Q: When I perform my Salaah alone (e.g. when I am ill), then do I have to perform my fardh Salaah in a loud voice?

Q: I would like to know the correct procedure of salaam at the end of Salaah. Is it Assalamualaikum warahmatullah or Assalamualaikum only?

Q:

1. My question is what surahs are the best to be read in witr? (I am referring to a Hanafi Madhad) Which or what surah is the best to recite in the first rakah, second rakah and in the last rakah.

2. Also is it permissible to perform one rakah witr after praying isha? And also is it permissible to perform 1 rakah witr in the dawn?

Q: In the last Tashahud, is the dua recited after durood or before durood?

Q: Can one recite any Surah repeatedly if the imam is taking too long to recite a Surah after Surah faatihah.

Q: Can one move the index finger during tashahhud? Most people don't move it once but keep on moving it. If one can kindly give me the refrence from Qur'an and Hadith.

Q:

1. If one happens to omits portion of Durood Ibraaheem due to one forgetting it or making a mistake, is the Salaah valid?

2. If one happens to recite Tashahud and one repeats the portion( Ash Hadu...) where the index finger should be raised, perhaps due to getting stuck, should one raised the finger twice?

3. If yes, and it was not raised twice, is the Salaah valid?

4. Whilst in Salaah, during Durood Ibraaheem, one adds the words "Sayyidina" before the words and Names Muhammed (Sallallahu Alaihi Wassallam) and Ibraaheem (Alayhis Salaam), is the Salaah valid?