History of CR 506.2a

Every distinct wording since 2010, newest first.

May 3, 2019 · War of the Spark
During the combat phase of a multiplayer game, there may be one or more defending players, depending on the variant being played and the options chosen for it. Unless all the attacking player’s opponents automatically become defending players during the combat phase, the attacking player chooses one of their opponents as a turn-based action during the beginning of combat step. (Note that the choice may be dictated by the variant being played or the options chosen for it.) That player becomes the defending player. See rule 802, “Attack Multiple Players Option,” rule 803, “Attack Left and Attack Right Options,” and rule 809, “Emperor Variant.”
January 25, 2019 · Ravnica Allegiance
During the combat phase of a multiplayer game, there may be one or more defending players, depending on the variant being played and the options chosen for it. Unless all the attacking player's opponents automatically become defending players during the combat phase, the attacking player chooses one of their opponents as a turn-based action during the beginning of combat step. (Note that the choice may be dictated by the variant being played or the options chosen for it.) That player becomes the defending player. See rule 802, "Attack Multiple Players Option," rule 803, "Attack Left and Attack Right Options," and rule 809, "Emperor Variant."
April 27, 2018 · Dominaria
During the combat phase of a multiplayer game, there may be one or more defending players, depending on the variant being played and the options chosen for it. Unless all the attacking player’s opponents automatically become defending players during the combat phase, the attacking player chooses one of their opponents as a turn-based action during the beginning of combat step. (Note that the choice may be dictated by the variant being played or the options chosen for it.) That player becomes the defending player. See rule 802, “Attack Multiple Players Option,” rule 803, “Attack Left and Attack Right Options,” and rule 809, “Emperor Variant.”
May 1, 2014 · Journey into Nyx
During the combat phase of a multiplayer game, there may be one or more defending players, depending on the variant being played and the options chosen for it. Unless all the attacking player’s opponents automatically become defending players during the combat phase, the attacking player chooses one of his or her opponents as a turn-based action during the beginning of combat step. (Note that the choice may be dictated by the variant being played or the options chosen for it.) That player becomes the defending player. See rule 802, “Attack Multiple Players Option,” rule 803, “Attack Left and Attack Right Options,” and rule 809, “Emperor Variant.”
February 1, 2014 · Born of the Gods
During the combat phase of a multiplayer game, there may be one or more defending players, depending on the variant being played and the options chosen for it. Unless all the attacking player’s opponents automatically become defending players during the combat phase, the attacking player chooses one of his or her opponents as a turn-based action during the beginning of combat step. (Note that the choice may be dictated by the variant being played or the options chosen for it.) That player becomes the defending player. See rule 802, "Attack Multiple Players Option," rule 803, "Attack Left and Attack Right Options," and rule 809, "Emperor Variant."
September 30, 2011 · Innistrad
During the combat phase of a multiplayer game, there may be one or more defending players, depending on the variant being played and the options chosen for it. Unless all the attacking player's opponents automatically become defending players during the combat phase, the attacking player chooses one of his or her opponents as a turn-based action during the beginning of combat step. (Note that the choice may be dictated by the variant being played or the options chosen for it.) That player becomes the defending player. See rule 802, "Attack Multiple Players Option," rule 803, "Attack Left and Attack Right Options," and rule 809, "Emperor Variant."
June 17, 2011 · Commander 2011
During the combat phase of a multiplayer game, there may be one or more defending
April 1, 2011 · Duel Decks: Knights vs. Dragons
During the combat phase of a multiplayer game, there may be one or more defending players, depending on the variant being played and the options chosen for it. Unless all the attacking player's opponents automatically become defending players during the combat phase, the attacking player chooses one of his or her opponents as a turn-based action during the beginning of combat step. (Note that the choice may be dictated by the variant being played or the options chosen for it.) That player becomes the defending player. See rule 802, "Attack Multiple Players Option," rule 803, "Attack Left and Attack Right Options," and rule 809, "Emperor Variant."
February 4, 2011 · Mirrodin Besieged
During the combat phase of a multiplayer game, there may be one or more defending players, depending on the variant being played and the options chosen for it. Unless all the attacking player’s opponents automatically become defending players during the combat phase, the attacking player chooses one of his or her opponents as a turn-based action during the beginning of combat step. (Note that the choice may be dictated by the variant being played or the options chosen for it.) That player becomes the defending player. See rule 802, “Attack Multiple Players Option,” rule 803, “Attack Left and Attack Right Options,” and rule 809, “Emperor Variant.”
October 1, 2010 · Scars of Mirrodin
During the combat phase of a multiplayer game, there may be one or more defending
June 18, 2010 · Archenemy
During the combat phase of a multiplayer game, there may be one or more defending players, depending on the variant being played and the options chosen for it. Unless all the attacking player's opponents automatically become defending players during the combat phase, the attacking player chooses one of his or her opponents as a turn-based action during the beginning of combat step. (Note that the choice may be dictated by the variant being played or the options chosen for it.) That player becomes the defending player. See rule 802, "Attack Multiple Players Option," rule 803, "Attack Left and Attack Right Options," and rule 809, "Emperor Variant."
February 1, 2010 · Worldwake
During the combat phase of a multiplayer game, there may be one or more defending players, depending on the variant being played and the options chosen for it. Unless all the attacking player's opponents automatically become defending players during the combat phase, the attacking player chooses one of his or her opponents as a turn-based action during the beginning of combat step. (Note that the choice may be dictated by the variant being played or the options chosen for it.) That player becomes the defending player. See rule 802, "Attack Multiple Players Option," rule 803, "Attack Left and Attack Right Options," and rule 807, "Emperor Variant."