To untap a permanent, rotate it back to the upright position from a sideways position. Only tapped permanents can be untapped.
July 3, 2020 · Core Set 2021
To abandon a scheme, turn it face down and put it on the bottom of its owner’s scheme deck.
May 3, 2019 · War of the Spark
In a Two-Headed Giant game, poison counters are shared by the team. If more than one player on a team is chosen this way, only one of those players can be given an additional poison counter. The player who proliferates chooses which player that is. See rule 810, “Two-Headed Giant Variant.”
April 27, 2018 · Dominaria
If a permanent or player chosen this way has more than one kind of counter, the player who is proliferating chooses which kind of counter to add.
September 30, 2016 · Kaladesh
Although transforming a permanent uses the same physical action as turning a permanent face up or face down, they are different game actions. Abilities that trigger when a permanent is turned face down won’t trigger when that permanent transforms, and so on.