Method of Salaah

Q: Can Surah Ikhlass be recited in the first rakaat and either Surah Falaq or Surah Naas in the second rakaat?

Q: What about specifically misprounincing the letter ذ as ز , ظ or the letter ث as س , ص ? For non-arabs the letters ذ , ظ , and ث are quote difficult to pronounce since these letters are prounounced with a lisp i.e bringing the tongue between the upper and lower teeth when pronouncing it. So the non-arabs because they are not used to the lisp sound read the same representative lettersound without the lisp. In such case is the salaah invalid either intentionally or unintentionally?

Q: Letters which have similar sounds like: ذ , ز , ظ does mixing up between them nullify the salaah? Also ت , ط and also ث , س , ص and also د , ض and also ح , ه and also ا , ع also ق, ك does mixing up between these letters nullify the salaah? I read that there a different views, but what is view that is to be taken ? And what did the majority say?

Q: If a person is incapable of making du’ā in Arabic during his salāh, may he make du’ā in any other language? I read that if he is able to make du’ā in Arabic, then there exists a difference of opinion in the permissibility of doing so in a different language while in salāh. According to Imām Abū Yūsuf and Imām Muhammad, it is impermissible and the prayer will not be valid.  On the other hand, according to Imām Abū Hanīfah, the prayer will be valid, but it is makrūh (disliked) to do so. Is this true? But the question is what if a person is incapable of making du’ā in Arabic during his salāh? Is it permissible without being makruh?

Q: What are the "Dua's" that Nabi (Sallallahu Alayhi Wasallam) read in last tashud after darood shareef? Is there any proof that Nabi (Sallallahu Alayhi Wasallam) used to pray "Rab be jaalnee mo qee ma asala tee............. " dua after darood shareef in Namaz?

Q:

1. Is it imperative to read diff rent surats each day in the five salaats? Would salaat be valid if one continuously recites the same surats only.  For example, in the Maghrib salaat each day, one habitually recites sura Falaq in the first rakaat and sura Naas in the second rakaat. 
2. Can Ayatul Kursi be recited in place of a sura in salaat or is it necessary to add at least two ayaats before or after ayaatul Kursi?

Q: If a person makes a sajdah on a warm hat which overlaps onto his forehead, will this be correct?

Q: Reading salaat behind Imam in jamaat, in the last two rakaat what should one recite, according to Shafii Maslak?

Q: Which is the correct method of making salaam at the end of salaah. Is it one salaam to the right and therafter one salaam to the left or does the face have to be brought back to the center after the salaam to the right and then salaam to the left.

Q: I have a question regarding Salaah. For eg. In Esha Salaah there are four rakaat's, in which two are audible and two are silent. What should we do in the last two rakaats?