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.

Performing Jumuah Salaah in the homes

Q: In the country where I live, many masaajid have been closed to the public and people are not allowed to perform salaah in the masaajid. Hence, in such a situation, can jumuah salaah be performed in people’s homes? If it is permissible, then apart from the two khutbahs that have to be recited before the salaah, what are the other important conditions required for the jumuah salaah to be valid?

The Islamic belief regarding sicknesses and contagious diseases

Q:

1. What is the correct Islamic belief regarding sicknesses, diseases, epidemics, etc.?  Are they contagious or not?

2. Please provide a detailed explanation of the following two Ahaadith narrated in regard to sicknesses,  لا عدوى ولا طيرة  - (there are no contagious sicknesses nor any bad omens) and فر من المجذوم كما تفر من الاسد-  (flee from a leper as you will flee from a lion).

It apparently seems as though the meanings of both these Ahaadith contradict each other.  What is the correct understanding and reconciliation of both these Ahaadith?

3. At the time of an epidemic, what is the Islamic teaching in dealing with people who are afflicted?

4. During the time of an epidemic, did the Sahaabah (radhiyallahu anhum) who were not afflicted attend the Musjid for salaah?