Ground Plane, Bypass Capacitors and Differential Pairs
imo, you did it completely wrong.  because:

what you did in both cases?  you traced one wire within each pair on one side of the board while other wire on the another side.  ascii-graphically it looks like so:

   a+  b+  c+  d+ 
   ==  ==  ==  ==
-------------------- top side
-------------------- bottom side
   ==  ==  ==  ==
   a-  b-  c-  d-


but any case you must keep both wires of a pair on single layer and when you change the layer for one wire in the pair you must do the same for the last wire as close as possible the first one.

in your case if you have less space, you can trace two pairs on the top layer and two pairs on the bottom one, like this:

  a+  a-    c+  c- 
  ==  ==    ==  ==
-------------------- top side
-------------------- bottom side
  ==  ==    ==  ==
  b+  b-    d+  d-


i shown no internal layers, but if you have those, you must route all the pairs over the analog ground plane/polygon. in other guidlines, follow the micrel's recommendation given in the appropriate application note(s).