This is an old philosophical chestnut. It is basically the same point as was raised by Heraclitus: "You cannot step in the same river twice".
However, I think there is a trick here, and it is easier to see it if we take a simple example.
Imagine that someone says, "I am not the same person as I was yesterday". Setting aside the question of whether this means physically, mentally, emotionally, etc., and just treating change in the abstract, we can see that there needs to be something in common between me today and me yesterday in order to establish change. For instance, if I changed completely (so that there was nothing in common between me today and me yesterday), then how can I still refer to myself as me? If "I" am completely differnt in every way (physically, mentally, emotionally), then what is there to link the two "I"s, and thus point to them and say "That one is a different version of that one".
Perhaps this is clearer if we look at a slightly different example. Tim is a person with certain physical, mental, emotional, etc., characteristics. However, one day he completely changes in every respect. So, now we are face with someone who has completely different physical, mental, and emotional characteristics. So, how can we say that Tim has changed if nothing is left of what made up "Tim"? It would seem more logical to say that "Tim has been replaced". The new person might be similar in some sense, but he cannot be Tim (because there is nothing that joins the two). For instance, even if we say, "Well, he is made up of the same (or most of the same) physical atoms", then THAT is what is the same.
So, in summary (and sorry for the long post, too), change would seem to be something which relies upon something staying the same. In this sense, it is what we might call a "relational concept" - its meaning is relative to something else (we change in relation to something that stays the same). Therefore, if 1 is true (nothing remains the same), then we cannot have change in any meaningful sense (though, I suppose we could have MEANINGLESS chaos).
However, I still don''t understand the phrasing of points 2 and 3.