...questions like "How hot is it getting there" you can easily answer yourself when you just search on google.com. And as all the others said, all your questions cannot be answered in general - it depends on the company.
If someone considers Qatar being a ggod place to live or not, is also depending on each individual person, there are no general answers to those questions at all. Some people spend more money, others less, the latter can save more then.
So get yourself a job offer and come back with specific numbers, this will make it possible to answer some (not all) of your questions...