Sajda-e-Sahw

Performing sajdah sahw after making a mistake in salaah

Q: I offered Isha prayer, but recited tashahhud between the two sujud in my second rakat. I decided to do sajdah sahw, but I forgot and completed my prayer. I was still facing the qiblah, but I removed my eye glasses, wiped my face and muttered to myself. Then I remembered to do sajdah sahw, and did it. Should I have done sajdah sahw? Will I have to repeat my prayer? 

Mistakenly reciting a surah instead of attahiyyaat

Q: Is Salaat valid in the following cases? If so, please advise what should be done if such an error occurs in the Salaat.

1. Mistakenly reciting thana twice.

2. Mistakenly reciting some Ayaats of a Surah, or an entire Surah, instead of tashahhud. Tashahhud is then recited after the mistake is  realized.

3. Mistakenly reciting some part of tashahhud, or the entire tashahhud, instead of Surah Fatiha. Surah Fatihah is then recited after the mistake is realized.