RE: Is The Future Predetermined?
I remember seeing an answer to this question when referring to the number of dimensions there could be in existence. If free will does not exist, and thereby meaning the future is pre-determined, then there are no more than 4 dimensions, because a 4th dimension would represent all of this universe's "eternity" in a sort of 4th dimensional solid object that encompasses all of everything that ever was, is, or will be, all simultaneously. The beginning and end of the universe and everything in between would all exist at the same time, much like the top and bottom of a ball in 3D space exists at the same time. To go beyond this, suggesting that there are more than one of those solid objects - in fact an infinite number of them to represent all the possible variations of them - would be what's required to introduce something we might identify as "free will", as there would be infinite number of options for any given scenario you could encounter.
I guess it's wrong to assume that just because something exists in a certain amount of dimensions, it cannot understand higher dimensions. 3-dimensional objects change through the 4th dimension which is considered to be time or as you stated: eternity. You cannot see time, and you cannot transform or "use" time, but you can "feel" it and are pretty much forced to "travel" because of it. You know some part of it, yet you are not "in" it yourself. A great feature of the human mind is that it can imagine impossible things.
The diagram does show how there are different paths for all of us to follow. We are the ones to choose which pathway to go down.