Treat each version of IG-88 as non-unique. (IG-88 does not stack. This ability works while in any game zone.)
When you deploy IG-88, your opponent may draw a card.
Bounty: When the battle phase starts, choose a unit in any arena or the build zone. You may rearrange the cards in that unit's stack.
Armor
IG-88's "treat as" text works even while IG-88 is in your deck, hand, discard pile, or face-down in the build zone.
IG-88's "treat as" text does not allow you to stack IG-88 at all.
Because you treat each version of IG-88 as non-unique, you may have multiple copies of the same IG-88 in play (even on your opponent's side). However, if all copies of IG-88 (B) are taken out of play by some means (discard, returned to hand, out of game, etc.), then all other versions of IG-88 on your side of the mat would immediately contest. Those on your opponent's side would contest with yours during the battle phase.
You may still finish building IG-88 even if your opponent chooses not to draw a card.