Tahajjud

Q: I heard that if one reads the last few aayats of Surah al Kahf and makes a niyyat to get up for tahajjud then it will be easy to get up. Is this true?

Q: My question is about tahajjud...

My mother often, not regularly, wakes up for tahajjud and offers tahajjud namaaz as she cannot do so due to her health. She offers it regularly in Ramadhaan, Shawwal, Muharram and Zil Hajj, etc. (special months). Me and my sister also offer tahajjud daily Alhamdulillah.

Recently, one of my relatives told my mother that if you have started offering tahajjud namaaz or if you offered it one day, you cannot quit it. It becomes fardh for you. I told my mother that this is baseless since a nafal namaz cannot become fardh but she wants to confirm it. Please clarify this according to the Ahle-e-sunnat sect. 

Q: Could you please inform me about the minimum rakaats of Tahajjud namaz and can I perform it about 20 minutes before fajr azaan? 

Q: Can we perfrom Tahajjud Salaah without sleeping because I am awake the whole night till fajar? 

Q: I want to know about tahajjud salaah, how can we perform tahajjud? 

Q: Is sleeping after tahajjud permissible?

Q:

1. Is midnight calculated as the halfway point between sunset and sunrise, or sunset and subh saadiq?

2. Is there some valid difference of opinion in the Hanafi Madhab on the above?

3. Is there more reward if witr is performed after midnight?

4. Is there more reward if tahaujjud is performed after midnight?

Q: Can we read tahajjud before heading to bed (time might be 11pm or 12 pm)?

Q: Can a hanafi follow the shabeenah namaaz?

Q: I would like to know if I can pray these 3 surahs in my tahajud salah; surah waqia, surah mulk and surah sajda because I pray out of salah so I can add them to my tahajud salah.