I am reading the book 'surface in 4-space' about the unknotting conjecture (Page 97): a 2-knot (2-sphere in 4-sphere) is trival if and only if the fundamental group of the exterior is infinite cyclic. 


It said that in TOP category, Freedman proved the statement is true. I don't know why it is also true for general surface. in top category? 



Is there a knotted torus in 4-sphere whose complement's fundamental group is infinite cyclic ?  
I have been avoiding addressing this since almost all that I know about the question is in that book. I don't recall exactly, but I think that Kawauchi showed that a torus with the fundamental group of the complement being Z is topologically unknotted. Recent work of Hillman <http://arxiv.org/pdf/1003.5408>
addresses some problems of 2-knot groups, but he deals with the spherical case. 


