the receiver must posses the ball all the way through even in the end zone. it's not like a RB who breaks the plain when he dives over a pile. even though he had control of the ball over the plane, it was not a catch until the 2nd act, where he posssessed the ball while on his back.
No because he took possession of the ball outside of the endzone and then brought the ball across to break the plane.If he took possession of the ball in the endzone then it would have been incomplete for not completing the entire act of the catch.