Qadha Salaah

Saahib-e-tarteeb forgetting to make qadha

Q: A person who is a saahib-e-tarteeb misses his Fajr and Dhuhr Salaah.

1. After he prays his Asr prayer, he remembers that he has not prayed Fajr and Dhuhr. Does he have to repeat Asr after praying the qadha of Fajr and Dhuhr?

2. He forgets to pray his previous day's qadha Fajr and Dhuhr and only remembers the next day after he has prayed his next day's Fajr sunnah. Should he now pray his qadha first, or pray the next day's Fajr fardh and then pray his qadha?

Repeating Esha fardh and sunnat if the fardh was invalid

Q:

1. If we perform Esha Fard, sunnat and witr and nafl but after the time of the prayer has expired we realized that the fard was not valid, what qadha do we need to offer (from the Fard, sunnat, witr and nafl)?

2. If we perform Esha Fard, sunnat, witr and nafl and before the time has expired, we realized that the fard was not valid, what do we we need to repeat (from Fard, sunnat, witr and nafl)?

Performing qadha of missed salaah

Q: I want to ask a couple of questions regarding qadha prayers.

1. What should be my niyaah when praying qadha namaz and what time of the day should I offer it?

2. How should I offer my qadha prayers, given that I have the following ones left? (I have only made an estimation, because I don't remember the count exactly): Fajr-4, Zuhr-6, Maghrib-1, Isha-Salaat-ul-witr of 2-2.5 years (around 800)

3. Do I need to offer all of the witr prayers or is there any alternative to it? I request you to outline the complete method, so that I can offer them as quickly as possible.