2) is a duplicate. Please see my answer to your other post.
3)
A graph passes through the origin if it is of the form y = bx (eg. y=2x +3 does NOT pass through the origin, but y=2x does)
A graph passes through a point if the equation is true when you put that point into it.
eg. (3,2) y = 2x --> 2 = 2*3 --> 2 = 6 so y=2x does not pass through (3, 2)
