Sajda-e-Sahw

Reciting a portion Bismillah and Ameen loudly

Q: If in salah on my own, I am reciting out loud and I recite bismillah out loud, and half way through it I stop, and re-recite it silently, is my salah invalidated? Also, is it invalidated if I recite it out loud and complete the recitation of it out loud only to re-recite it silently? I also have the same question but instead of Bismillah, I recite ameen out loud. Does reciting ameen out loud invalidate the prayer? also, if it does, would rectifying the ameen out loud by reciting it again straight after silently, cause the prayer to be valid again? Another question I have is that during the salah, I said some of the takbeers out loud and others including possibly 'Sami Allahu liman hamida' silently. Would this inconsistency render my salah invalid?

Reciting the same Surah in two rakaats

Q: During Salah, if one recited a particular Surah after Surah Al Fatiha in the first rak'ah (for example, one recited Surah Al Kauthar), and then in the second rak'ah, after reciting Surah Al Fatiha, one begins to recite Surah Al Kauthar and then realises that he has already recited this Surah in the first rak'ah, and so he immediately starts again by reciting a different Surah (for example, Surah Al Ikhlaas). Does this action require sajdah sahw, since he was reciting a particular Surah, then stopped, and started again by reciting a different Surah?

Performing five rakaats

Q: I prayed asr or Dhuhr I think, and I think in 2nd rak'ah I said ayah of al Faatihah wrong but was not sure so I ignored it and on the third rak'aat I noticed it was probably wrong so I took the 3rd rak'aat as 2nd and finished like normal and then did 2 sujood sahw. Any thing wrong with this?