Qadha Salaah

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?

Q: My husband passed away last year. The total of his missed salaah in his lifetime is 29 132. He asked that this be paid from his estate. If I cannot afford to pay this amount, what should I do?

Q: I have heard that one should pray Qadha prayer in solitude so that it should not be revealed to anyone that one is praying Qadha prayer. Is this true? 

If so, then there is a problem that in a house where one does not get solitude and it is not possible in the mosque, then what should one do in such a case? 

Then can one pray Qadha prayer in front of the family members or in front of everyone in the mosque.