[Big Bang] Adventurer Skill Tables/Notes

I wonder if anyone knows how do these 3 skills work?

1. Mortal Blow : Does it work on boss mobs? (BigFoot, Anego, Samurai Knight)
2. Vengeance : How does one activate this skill? or Issit passive like Final Attack?
3. Hamstring : Does it work on boss mobs? (BigFoot, Anego, Samurai Knight)

Thanks !

Greatly Appreciate.

From what i know:

1. No because that would be hax
2. no one knows because there haven't been videos of it being used? One would expect taking touch damage = push back effect. Passive.
3. highly likely it doesn't work on bosses at all like pre-BB.