Various Masaail on Qadha Salaah

Q: Does qadha namaaz exist? Some people say the the prophet (Sallallahu Alayhi Wasallam) has not said anything like replacing a missing prayer. If it exists, when does maghrib namaaz become qadha?

Q: I have missed many namaaz in the past (as per my calculation 17-18 years namaaz). Now for the last one year I am regular in it. My question is regarding my qaza namaaz. I read that I have to perform my qaza farz namaz too. I read a short procedure of performing namaz too, in which I have to recite single time Subhana Rabial Azeem and Subhana Rabial Aalla only once, in Attahiyat short Darood shareef and in 3rd or 4th rakat Subhana Allah 3 times instead of Surah Fatiha, and Rabigfirlli 3 times instead of dua Kanoot. Is it valid? Do I miss my sunnatul Mukada and pray my qaza namaz and complete it as early as possible and then start praying my whole namaz after completing my all qaza namaz?

Q: When having multiple qadha salaah to read, what is the shortest way to read a salaah (if these are present, it's counted as done)?

Q: My wudhu broke whilst performing qadha Salaah. Must I perform two Salaahs to make up for this i.e. one for the recent broken qadha and another for the initial qadha?

Q: I am 30 years old. I started offering Salaah on time at time. I want to make qadha for the past 23 years. How can I offer qadha of those Salaah?

Q: We get 15 minutes for sunnat in Asr Salaah. If someone has missed his Fajr and Zuhar Salaah, then can he offer his farz salaah of Fajr and Zuhar instead of offering Sunnat Ghair Muaqqedah of Asr in that 15 minutes?

Q: I know that if you miss a waajib in prayer, you must perform sajdah-e-sahw, and if you fail to do so, you should repeat the prayer, so long as its time remains. However, once the time for the prayer is over, the prayer is not to be repeated. What is the status of missing a waajib act in a qada prayer? If you miss a waajib in a qada prayer, and you failed to perform sajdah-e-sahw (or you performed sajdah-e-sahw incorrectly, i.e. you made only one sajdah), do you then have to repeat that qada prayer? Is it merely recommended to repeat that qada prayer or is it waajib to repeat that qada prayer?

Q: This morning I was going to wake for fajar and heard the namaz and saw someone else in the bathroom so I closed my eyes and waited. I didn't realise that I fell asleep and when I got back up it was still dark so I rushed to the bathroom to make wudhu. I am a very doubtful person so making wudhu takes some time but I am trying to get better and did it as fast as I could. When I came back I looked outside and it was still a dark blue and there was little  yellow in the far back so I quickly started praying. I didn't think it was that late as fajar happens around 6. I thought it might be 6:30 at the latest but after I prayed 2 sunnats I checked my phone and it was almost 7. So I finished my namaaz. I know it is bad to delay prayer and I didn't mean to. I am so worried I might have prayed in the forbidden time but I remember reading that if you didn't mean to delay fajar prayer you can pray as soon as you remember or wake up so did I do the wrong thing? How do I fix this?

Q: I have lot of qadha namaaz. Can I read ishraaq, chashth, awwabeen namaz? I have lot of fear. How can I overcome this?

Q: I have just found out that I calculated my haidh incorrectly for many months due to regarding a normal discharge to be blood. Do I have to offer qadha salaah for all these months? And what is the status of the salaah I offered while I was impure? Please advise.