2 Yes it is outboard of the sparkplug it pumps air in the exhaust just after the exhaust valve to help with emissions. It also causes your exhaust to be hotter and makes pipes blue.

3 Uni filter is a replacement for stock that is a little better and washable so you can reuse it.

I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!