Witr and Nawaafil

Performing Tahajjud Salaah in pairs of 2 and 4

Q: We know that praying 8 rakaah in tahajud is sunnah but there is no limit on the number of rakaah.

My question is should we pray these 8 rakaah in pairs of 2 or 4 and if we want to pray in pairs of 4 for example 4+4 is 8 so should we recite another surah after fatiha in the third and fourth rakkah because we know that reciting a surah after fatiha in the third and fourth rakaah is wajib in sunnah e muakadah and ghair e muakadah.

Tahajjud

Q: I have some questions regarding tahajjud.

1. How long before fajr does the time for tahajjud end?

2. What is the sunnah method for performing tahajjud?

3. How do I pray tahajjud during haidh?