Muay Boran is an army combat system and a predecessor of Muay Thai.
Muay Thai is a “sportified” version of Muay Boran with different rules and slightly different fighting techniques.
You can think about Muay Thai as of a bit softer version of Muay Boran with boxing gloves that was created for ring competition and not for a XVI century battlefield.
For more information read: History of Muay Thai: from Muay Boran to modern Thai Boxing
In Muay Thai you condition you shin by kicking Thai pads and heavy bags. You start with pads and heavy bags and then progress to kicking banana bag once your shins are tough enough to do so. After a few years of conditioning your shins with banana bags they may be hard enough to break a baseball bat.
Read more about Muay Thai conditioning
Yes, it is. As a matter of fact when a proper flying knee makes a contact with an opponent’s chin it’s an instant KO. You may be in trouble if you miss with a strike cause after landing on a ground you’re vulnerable to counter attack.
All in all, you can win more than you can loose if you good at throwing it.
Read more about an Advanced Muay Thai moves and techniques
You should wear a black tank top and a gold flamboyant Lumpinee Muay Thai shorts :-)
Seriously though, most of the good gyms will provide you with vest and shorts with gym emblems.
Most of them will even have a gear which you can borrow for training which I don’t recommend you to do unless you’ve got no other option. The thing is that if you’re serious about your training you should bring your own gloves and elbow/shin pads. I wrote a post about what kind of gear you’ll need for a training and what to look for when buying it.
Check this post to learn how to choose the right Muay Thai Gear
It depends whether you are planning to become a pro or an amateur fighter. It also depends whether you are already physically fit and can start learning techniques straight away or you have to start from a scratch and build up strength and stamina before you do anything else.
A philosophy of a Muay Thai, which you can trace to Thailand and Thai traditions, is based on competition: to prepare fighters to compete with the others, to be a ring ready fighter. Muay Thai gyms will follow that philosophy. In most of the good gyms a great pressure in put on sparring and full-power sparring as a main tool of teaching (and learning).
Like you probably know, there is no belt system in Muay Thai so instead of an inter gym competitions will give you the sense of progress and an achievement.