Qadha Salaah

Q: If I read salaah and then realised I never had wudhu, how should I repeat it? Will I need to read my sunnats again or only fard and waajib?

Q: During my early youth days as a baligh teenager, I was regular with my salah. However, my brother used to make me laugh in my salah after which I knew it broke my salah and I would repeat the salah but not the wudu as I did not know for years that this breaks my wudu. Would I need to make qadah of these prayers ?

Q: My grandmother passed away some years ago. During the final portion of her life (approximately two years), she suffered from dementia, due to which she would be very confused as to what day it was, whether she had eaten or not, etc. At this time, she stopped performing salaah as well. My questions are: 

(1) Does fidyah need to be paid for the all salaah she did not perform during the period she suffered from dementia? 
(2) If yes, can the fidyah be paid from her estate/wealth? 
(3) If the fidyah cannot be paid from the estate, who is responsible for paying it?

Q: Alhamdulillah by the mercy of Allah, I have been consistent with my salaah with Jamaat for many years, and have no qadha from the age of 17 onwards. However, before that unfortunately I used to miss most of my Salaah. 

My family wants me to go for Umrah but I don't feel it to be the right thing for me to join them, as I haven't completed my qadha salaah yet. I feel it's doesn't make sense to do that great but nafl amal when a compulsory amal is outstanding. I would feel extremely uncomfortable visiting the Kabah Shareef and Madinah, including the mubarak qabr of Nabi (sallallahu alaihi wasallam), and then conveying the durood with such major sins and unpaid debt on my shoulders. I understand that there is obviously barakah in Umrah, but there might be barakah in making qadha salaah as well (in my opinion). 

In addition, I find that my concentration and devotion to any nafl amal is weak and I always feel that I'm wasting time since I'm not prioritizing what is more important in the sight of Allah. Please advise.

Q: If a person is performing Nafl Salaah and he makes several intentions, and thereafter he breaks his Salaah or it is nullified, what is the method of Qadha?

Q: If you have missed salaah for years but are now unable to make them up (qadha) because you are sick, what should you do? Is seeking forgiveness enough?

Q: When performing multiple qadha salah, does the qadha of the Witr have to come after the Isha qadha? 

Example, you must perform the 4 rakats of Isha and then the 3 rakaats of Witr? Or is it permissible to read multiple sets of the qadha of Isha and then multiple sets of the qadha of Witr? So you read 4 rakaats a few times and then you read 3 rakaats a few times

Q: Do I have to makeup for salaah if it was led by a child who is not a mukallaf?

Q: I had many qadha salaahs and I had made the qadha of my witr salaahs before all my esha salaahs. Will the witrs have to be repeated, and if so, must I repeat just the witrs or the eshas as well?