Salaah

Q:

1. I have been told that if, for example one reads surah Nasr in the first rakaat, then in the next rakaat one cannot read surah Ikhlaas - it has to be the next surah, or a gap of 2 surahs. Please clarify this rule for me (e.g., does it apply only to short surahs, does it apply to 4 rakaat salaah as well, etc.)
2. For long surahs, can one read from different parts of the surah in consecutive rakaats. Eg., 1st rakaat beginning verses of surah Najm, and 2nd rakaat ending verses of surah Najm.

Q:

1. If one is late for fajr jamaat, and performing the sunnats will result in missing jamaat, what should one do?
2. Can the sunnats of fajr be performed after the fardh? I have noticed some brothers doing this?

Q: What is the ruling regarding lying down after the two sunnats of fajr in the Hanafi madhab?

Q: When I pray salah I don't remember how many sajda I do if I did 1 or 2 sajda.  If I can't remember how many sajdas what shall I do?

Q: Can a person read the following Dua in his Fard Salaah:  حمدا كثيرا طيبا مباركا فيه after reading: ربنا و لك الحمد, in ruku', similarly can he read in jalsah: اللهم اغفرلي و ارحمني و عافني و اجبرني و ارزقني and if he is a muqtadi can he read these two dua's?

Q: What is Salaat-ut-Tasbeeh and when and how to perform it?

Q: I understand that if one laughs aloud in Salaah, his wudhu breaks, and if he laughs silently, only his Salaah breaks. However, I wish to know what constitutes a loud laugh and what constitutes laughing silently. Also, is a smile considered laughter?

Q: If "Rabbanaa lakal hamd" the word hamd at the end is sounded as a ت and not د will the salaah brake? The letters ت and د are they from same makhraaj, and so there is no zallatul qari is these are replaced by eachother not on purpose?

Q: I read in a book that to read Sami Allahu liman hamidah, to read hamidah with a soft h i.e. a ه will break salaah. Why is that? The meaning is changed? What if it happened unintentionally?

Q: I am 7 months pregnant and suffer from backaches and leg pains. Will it be permissible for me to sit and read salaah when the pain is very severe?