Salaah

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?

Q: Question regarding reciting inaudibly. In my case I was praying Dhuhr Fardh and quietly as to hear my own voice, in my last (4th rak'ah) - I was reciting "Ghayril Maghdoubi" at Maghdoobi, I could only clearly hear "Ma--doobi" the Gha wasn't proper so that I could hear, but I moved my tongue to recite it as normal. Obviously I didn't want to recite "Ma--doobi", so I think I inaudibly said the gha, does this matter or affect the validity of the namaz?

Q: Is it ok to sleep before esha and then wake up and perform Isha before the morning? Is it right to perform Isha at 1 o'clock? 

Q: What is the difference between Qiyaamul Layl and Tahajjud? Is it necessary to sleep before offering Tahajjud or can one perform it immediately after Esha?