Method of Salaah

Q: Is it permissible to read surah qadr in the first rakat of salah and surah bayyinah in the second. What is the number of aayats that make a surah longer than another one?

Q: I just want to ask when is the perfect time to make du'a? Is it after salaah? I mean after you make tasbeeh or after performing sunnatul muakadah?

Q: In the second rakaat of any Salaah, can a longer Surah be recited compared to the Surah recited in the first rakaat? Or must the Surah recited in the first rakaat always be much longer than that recited in the second rakaat? If so, on what basis should the length of a Surah be determined? 

Q: When performing salaah sitting on the floor, and going into ruku, how far down should one go down?

Q: In a four rakaat sunnah salaah, if a person reads Surah falaq and naas in the first 2 rakaats, is it fine to read surahs before that thereafter, such as Surah wal aadiyaat and qariah?

Q: In a 4 rakaat Sunnah salaah, if in the first 2 rakaat one reads e.g. 1 page in each rakaat. Is it fine in the 3rd and 4th rakaat to read 1.5 pages? I.e more than the first two.

Q: Whilst performing a Qada prayer, one had just finished reciting "As-Salamu-Alaykum" of the first Salaam, and before one could complete "Wa Rahmatullah" (and even before the second Salaam), one's wudhu broke. Is this prayer to be repeated?

Q: Can dua be made in Sujood after having prayed the fardh Salaah?

Q: After ruku I used to say sami Allah huliman hamida (without ha in the end) and no Ayn at Allah, will this make my salah invalid?

Q: I want to know what are the faraaidh of Salaah?