The card with cipher remains encoded on the chosen creature as long as the card with cipher remains exiled and the creature remains on the battlefield. The card remains encoded on that object even if it changes controller or stops being a creature, as long as it remains on the battlefield.
May 3, 2019 · War of the Spark
A creature can’t have a greater power or toughness than a noncreature permanent.
January 25, 2019 · Ravnica Allegiance
A creature can't have a greater power or toughness than a noncreature permanent.
February 1, 2014 · Born of the Gods
A creature can’t have a greater power or toughness than a noncreature permanent.
July 13, 2013 · Magic 2014
A creature can't have a greater power or toughness than a noncreature permanent.