How can I type on this keyboard?
This device isn't meant for typing, think of it as a gaming controller. That's why it's called a keypad.
Why is the lefty layout a reversed qwerty?
The mirrored layout stems from the fact that the right and left hand are "mirrored" between each other; by reflecting the keys that right-handed users press with their left hand it allows left-handed people to use the default layout and key-binding of games and the same hand-movements (specular) that right-handed people normally use.
Is there a version for right-handed people? Is the PCB reversible?
Yes, you can assemble all components on the opposite side of the PCB as well as the case plates, and use the default layout. The result will be a device that you can use with your left hand. (regular qwerty layout)
What games can I play with it?
It can work for any game, but it works best with first-person or third-person games. I do not recommend it for games where you don't use the mouse (both hands on the keyboard).