Is there not the possibility of traveling from one point in three dimensional space to another within a period of time lesser than that which would be required in the three dimensional universe by entering, for example, a four dimensional universe, and ?bypassing? the curve or other indirect 'passage' from a to b as we could two ends of a curved two dimensional surface in 3D space?

If there are more than 4-dimensions it is conceivable that something like that is possible. Worm-holes for example can give rise to situations like this. (these don't require extra dimensions).

 

Such situations could lead to time-machines as we have apparent faster than light travel.

 

You should do a search for worm-holes and warp drives in the arXiv.

Wormholes would involve the folding andjoining of areas of our own universe?

arXiv seems to be a good source, thanks