1.) Basically all of them are made in factories and exactly how you would imagine in your head (see pic)
1a.) Retribution and Cryx Jacks are made differently, don't know much so google it.
2.) The Warcasters (powerful battle wizards) control them over something called the cortex. The cortex is a magical-mechanical brain that allows those with the Warcaster spark to control and enhance them in combat.
3.) With some kind of motor or oven. It can be steam, coal or how cryx does it, souls.
4.) cortexes make them as intelligent or a smart dog, so they can be trained to a minor degree (Jack Marshals for example are people who can control jacks despite not being Warcasters by giving them orders and commands).
5.) Yes, cortexes develop and learn over time, which is why old jacks that are assigned to specific Warcasters over and over absorb part of it's controllers personality. It's even possible for them to develop traumas.
6.) No, not without help from outside. The elves of Ios for example have self-regenerating energy shields. Convergence Vectors do, but they are technically not warjacks.
7.) Cryx has jacks formed as birds and spiders, though most all of them are humanoid.
8.) Depends on the faction. The whole point of warjacks, is that they are strong enough to carry weapon which would be too cumbersome and/or big for normal humans to carry, so they are very strong (in terms of profile, a human has an average Strength of 5, while a Warjack's goes from 10 upwards).
9.) The first Warjacks are called Colossals and were made by the human nations of the continent to free themselves from a race called the Orgoth, who conquered the land with evil magic. The colossals were abandoned due to their impractical sizes and turned into the smaller warjacks. As to who and why, the Dwarfs of Rhul showed humanity how to build cortexes.
10.) Yes. Warjack is basically just the term for "weaponized Steamjack with a smarter cortex". Laborjacks are common in most nations.