Sajda-e-Sahw

Reciting thana in place of dua-e-qunoot

Q: On pg 217 beheshti zewar, masla 32. Mention is made of a person who instead of reciting dua e qunoot in witr, read thanaa, then later read the qunoot, no sajdah sahw is required. If he doesn't read the qunoot later, ie just reads thanaa or something else in the dua e qunoot, will sajdah sahw be wajib? The kitaab mentions dua qunoot is wajib. Like surah Fatiha. If one reads something else instead of Surah Fatiha sajdah sahw is wajib. Please can mufti sb explain why for the qunoot it is not the same?

Reciting "rabbigh fir li" between the both sajdahs

Q: In regards to saying dua between two sajood during prayer; I contacted local Mufti and received fatwa that reading dua between two sajoods during prayer (Rabigh Firlee) is against the Sunaha of Prophet (Sallallahu Alayhi Wasallam); so there is no need for sajada-e-Sahu if someone don't read dua between two sajoods. I am 35 years old and never read Rabigh Firlee between two sajoods but during Hajj last year; I read in a book that of someone don't say "Rabigh Firlee" between two sajoods then he has to perform Sajad-e- Sahu and since then I am saying this dua between two sajoods. But after I contacted local Mufti for authenticity of this dua; he advised that it is against Sunnah. Please clarify.

Doubting the number of sajdahs performed

Q: I was praying and I got doubts about how many sajdahs I did and I was doing first the Tashahhud and I determined that I would do one more sajdah in case and I was reciting "Assalaamu alayka ayyuhannabeyyu.. " and around here or after "wa" I determined that I was going to do sajdah, but I added "wa Rahmatullaah" and then I stopped and proceeded to do sajdah (I did Sajdah-Sahw afterwards). But now I doubt that I did an "addition" that invalidates the salaah.