What happens when a double-sided card is returned to the battlefield or a copy of it appears?
It will come back as the Garruk Relentless with 3 loyalty counters since it enters the battlefield as a new object. See comprehensive rules 110.6 and 110.6b


  110.6. A permanent's status is its physical state. There are four status categories, each of which has two possible values:
  tapped/untapped, flipped/unflipped, face up/face down, and phased
  in/phased out. Each permanent always has one of these values for each
  of these categories.
  
  110.6b Permanents enter the battlefield untapped, unflipped, face up, and phased in unless a spell or ability says otherwise.