I think the true definition of a #1 is someone who is going to be the go-to guy in any occasion; Deep, short, across the middle, when they are doubled, it shouldn't matter. A true #1 WR should be the guy you want to have the ball in his hands under any circumstances. That's why most #1 Wr's lead their teams in rec. (I said MOST). Because their teams can trust them to make a play therefore they get more attempts thrown their direction.
When these receivers perform the way the above is specified under ANY condition then they are paid better.
So I guess #'s 1,2 and 4 are correct.