1-Depending on its altitude and velocity it would either be a satellite or a fire ball on re-entry.
2-If it were travelling at the speed of light upon return the pilot would be much unger than his twin on earth.
3-If it incounter a worm hole it could theoretically return before it left-providing it did not encounter anti-matter.
This question would better be answered by Stephen Hawking
Stephen Hawking, The Big Bang, and God