Board Thread:Questions and Answers/@comment-158.222.169.246-20160712071824/@comment-26447088-20160713031900

Unique skills awaken only at the start of a quest (first wave). Like how Passives unlock at the start of any wave of a quest (with the exceptions of Belly of the Beast events, Call to Arms/Action events, and Rifts), except Uniques are restricted to the first wave.

I'd suggest checking out the guide found at http://ishtaria.freeforums.net/thread/2904/quick-guide-platinum-units where they give a tip on how to unlocked Uniques. Uniques work like any other Rush/Multi/Passive skills in how likely they are to awaken; the higher the loyalty the better.

Kill shots are defined as the user above my reply posted: Kill Shots = the killing blow on a monster (or unit in CtA) or Overkills (as indicated by the text at the right side of the screen when you deal damage to a monster with an empty Health Bar).