Uppy-downy turn 1 written clarification

Do I have it right that a GK unit with deep strike & Gate of Infinity rule can start on the battlefield, and, if I go 2nd he can Uppy-downy my 1st turn, 9" from enemy models? If so, where is it written clearly that it's viable turn 1 so I can resolve the issue if an opponent thinks that's not correct?