How...what....

Excluding legendary tier stuff, it is possible for a rare item on the 2nd or 3rd line to have epic or unique lines. Same with Epic items to have their 2nd or 3rd lines have unique lines. This happens very rarely.

As for legendary lines on rare/epic/unique items, no one has shown any proof yet. My opinion is it isn't possible.

I have seen a rare shield with 6% def first line