In full editor use below settings in replacebycode sample.
var editor = CKEDITOR.replace( 'editor1', {
//allowedContent : true
enterMode : CKEDITOR.ENTER_BR,
toolbar : [
['Font', 'FontSize'], ['TextColor', 'BGColor'], ['Bold', 'Italic', 'Underline', 'Strike'], ['Subscript', 'Superscript'],
['JustifyLeft', 'JustifyRight', 'JustifyCenter', 'JustifyBlock'], ['NumberedList', 'BulletedList'], ['Outdent', 'Indent', 'Blockquote'], ['Table', 'HorizontalRule', 'SpecialChar'], ['Link', 'Unlink', 'Image'],
['Cut', 'Copy', 'Paste', 'PasteText', 'PasteFromWord'], ['Undo', 'Redo', '-', 'Find', 'Replace', '-', 'SelectAll', 'RemoveFormat'], ['Source']
]
} );
Notice that Justify plugin is disabled no matter what you click on. As discussed with @Rainmar this is because Justify Plugin adds only P to ACF while in other modes (BR and DIV) elements are "wrapped" in DIV when justified (block elements aren't but this rather doesn't change anything). To solve this in other modes, Justify should report DIV to ACF.
Pushed t/10320 on dev and tests.