On short connections [closed]

There are many questions of the type "I have to change at airport X, is Y minutes/hours/days enough?" in this forum. I understand that the usual answer is "If you booked your flights on the same ticket, the airline is responsible in case you miss your second flight." This raises some questions in me. Assume I booked two flights on the same ticket.

1) Are airlines generally good in making flight plans such that one would rarely miss flights? More precisely, are there any statistics how often people miss connecting flights (per airline)?

2) What kind of traveller do airlines assume when they make flight plans? E. g. old people/people with handicaps would probably need more time than young, fit ones. Do airlines (try to) plan as much time as very disabled people would need?

3) What am I allowed to do in a stopover so that I am eligible for a compensation flight? What if I need to go to the bathroom and miss my flight because of that? Is the airline responsible? What if I go shopping/do not run/go to a prayer room/am an analphabet (and can thus not properly read signs) etc.? Are there regulations what I have to do/am allowed to do to be eligible for a compensation in case I miss my flight?

4) Is it "easy" to get a compensation for the second flight in case I miss it? For example, I would say it's rather hard to get compensation for cancelled flights - I have the feeling that many people are not told that they are eligible for compensation, that it is often quite hard to reach airlines and there are even companies fighting for your money! It is sometimes/often the case that people have to go before a court to get their compensation flight/the money for it?