Various Masaail on Qadha Salaah

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.

Does one still have to make up for qadha salaah after performing hajj?

Q: If one has made Hajj and and during Hajj one made sincere taubah for missing previous salaah and since Hajj one has never missed another salaah, do you still have to repay your outstanding salaah that was incurred in the years before your Hajj? I am asking because I read that the person who performs Hajj emerges sinless (all sins forgiven) like a newborn baby, and sincere taubah was made for missing previous salaah. 

Making up for salaahs missed while one was an apostate

Q:

1. As a youth, someone made an oath to not do something and they did it, they then fasted 3 days to expiate the oath (as they were unable to do anything else). Later that person apostatised from Islam but came back to the Deen. Do they have to redo the expiation for the oath broken? No oath was made since that time. 

2. Also, in terms of salah missed, are salahs missed over years must be made up by someone who Apostatised but later came back to the Deen?