Ok, if I do damage to a plainswalker with a cipher encoded to a creature would the effect take effect
I'm afraid not. It only triggers when you deal damage to a player. From the Comprehensive Rules:
702.97a Cipher appears on some instants and sorceries.....that creature has 'Whenever this creature deals combat damage to a player, you may copy this card and you may cast the copy without paying its mana cost.'"