Salaah questions

Bismillah hir Rahmaan nir Rahim,
Namaaz Hanafi
1) I am Hanafi, what is the latest time that Zohar can be read till, is it till when Shafi Asar Bigins or when Hanafi Asir bigin or another time, kindly specify?
2) If one begins the first rakaat of Asar and the magrib azaan goes then is it considerred as a Kaza.
3) What happens with Fajr if one begins the first rakat before sunrise and the while reading the sunrise time sets in what is the position in this case