surah naas

Qiraat in salaah

Q:

1. Is it compulsory to recite Tasmiyyah before Surah Fatiha in the 2nd, 3rd & 4th rakaats of Salaah.

2. If we mistakenly recite Surah Naas in the first rakaat of Salaah, how do we continue with the rest of Rakaats? Will Sajda-e-Sahw be compulsory?

3. If I mistakenly recite a Surah in the second rakaat which is earlier in order to what was recited in the first rakaat, should an additional latter Surah be recited if it is realised within the rakaat?