Incorrect. In dual-swords style it's better if you use two short swords to prevent collision between your two swords.
No. People would say their technique names before performing it.
Like Roronoa Zoro?. Sword grip is designed to be wielded by hand. So you cannot wield the sword by your mouth properly. Also the sword weight would cause big problem. If you want to use mouth to wield sword, you need to use the ultra light weight sword that made from composite and with grip that specially designed for mouth.
When you stab your enemy, the knife would also press your head and cause injury. So you need to wear steel helmet and place the knife on your helmet.
Of course you can use long Katana with only one hand. But it's easier if you use two hands as Katana was designed for this method of usage. Katana from classical Samurai era were heavy enough.
In the classical samurai era, before they use Tanegashima rifle, the fighting in battle was based on rank, ordinary infantry with ordinary infantry, samurai with samurai. When a samurai would duel with another samurai they would introduce each other. They did not say about technique, but they said about their clan and their ancestors reputation.
Fiction often different than reality. In real fighting there are no fighters who do this.
I like Kendo now, excluding the bowing and stuff. Lets fight, Kiro!
Let there be baths of Tomato in Jannah!
Brothers! This is how I want to fight in Jannah, but much more interesting and bloody. (Mute cuz it is possibly/probably sound-effects/instruments.)
Will Allah allow me to do war in Jannah (against/with people who want to, I don't like to attack people who do not want to.)
They are more like good friends rather than villains. 
mg: