It's complicated. And they are still made. Organ building uses many disciplines including wood working, Metallurgy, electricity, to name just a few.
One could argue that electronic organs that mimic the sounds of pipe organs are their descendants, but in truth, pipe organs are still in use today, mechanically, as pipe organs.
Pitch is directly proportional to the size of the pipe.
There is no short answer to this. Entire books have been written on the subject. The Wikipedia article on Pipe Organ has a section on Baroque and Renaissance organs.
Pipe organs
In general yes. There some very small portative pipe organs that might be smaller than a large harmonium but in general pipe organs are larger than harmoniums.
pipe, electronic, and reed organs. also a harmonica is a mouth organ.
You can get grant money to restore pipe organs from various sources. Most corporations and organizations will offer grants. You can look for a corporation that will identify with your need to award you the grant.
Pipe organs have different sized pipes because they can then make different sounds.
No. A concertina is a type of accordion. Even the smallest pipe organs are larger than a concertina.
It is the name of a family in Quebec which makes famous pipe-organs.
Asbestos pipe is made of cement that contains asbestos fibers. Iron pipe is made from cast iron.
This question is too vague. There are thousands and thousands of pipe organs world wide. The first pipe organ? No one knows. The history of the organ goes back to at least 300 BCE and probably much earlier.