A German ISOT (1912 to 1942)

  Well will Stalin stop at the Pyrenees is possibly the big issue?  The Red Army isn't that efficient at this point and its lost a lot of its regulars who had some training and experience.  However its a 1941/42 force.  The German 42 army outside the ISOT is still sizeable and of generally high quality but is now cut off from virtually all supplies and equipment.  They still have Austria and Bohemia but otherwise can only rely on 1912 technology - or what they can loot from already occupied territory.  I doubt this would be enough to replace the material losses they will be taking and possibly not even normal wear and tear so those motorised/armoured units and a/c will quickly fade away as will a lot of the other weapons they have, which didn't exist in 1912.

  Germany 12 has a lot of men in a powerful military, by 1912 standards but its going to be cannon fodder when faced with 1942 artillery, air power, armour etc.  It can try and link up with the rump of Nazi Germany, although there's going to be some awkward relations between the two but I doubt the latter can supply more for the 12 army let alone train them up for modern war.  There are the assorted Axis powers and allies, Italy, Romania, Hungary etc and their probably more powerful militarily than Germany 12.  They could hold off the Soviets for a while but that's probably expressed in months.

  Possibly Germany 12 might seek some terms to surrender to the western allies.  However even if their willing to do this the allies aren't in a position to send more than minimal forces.  Britain has been drained by the war so far and facing a developing disaster in the east with the Japanese attack while the US is still only really starting to build up a substantial army.

  One complication here with Germany 12's colonies having reappeared.  That will cause confusion across parts of Africa and also the SW Pacific.  The Japanese will suffer here as well as a number of their bases and the forces there have suddenly disappeared but how much that would affect their drive south I don't know.  Ironically the German East Asia fleet and its base at Tsingtao will have reappeared and will cause some initial confusion which will probably end violently.  They won't last long but will distract Japanese attention a bit and also cause some tension with imperial Germany.  However it also means that British/Commonwealth forces and bases in locations such as Rabaul and Papa New Guinea will be lost.