He doesn't copy whether that creature is tapped or untapped, whether it has any counters on it or Auras and Equipment attached to it, or any non-copy effects that have changed its power, toughness, types, color, and so on
If you control more than one legendary Sliver with the same name and the "legend rule" begins applying to them again (perhaps because Sliver Gravemother leaves the battlefield) you'll immediately have to comply with the rule and put all but one of those Slivers into the graveyard
Having three box toppers make a display box purchase a great value
Everything that is specified by the effect creating the original token or tokens will also be true about the additional token or tokens created by Parallel Lives's replacement effect
Doubling tokens with Anointed Procession is always powerful in this kind of strategy, and there are plenty of red cards that can make token copies of your creatures until the end of turn