It seems that the vast majority at my school did Question 3; I did Question 4, though. A couple only revised Weimar Germany so were obviously not in a very good position to do the paper!
I thought Question 4 was relatively open ended and didn't really suggest a structure (i.e. it was ambiguous as to if it was referring to the war causing the Nazi regime to be stable or unstable). If it helps anyone, I talked about the following (hopefully should be okay):
1st part) How WW2 made Nazi regime stable: despite rationing they were able to obtain luxury goods from captured countries -> high morale, Hitler had majority of German's support in 1940; gave people of Germany a patriotic cause to unite behind so supported Nazis; rearmament in preparation for WW2 was very good for economy -> stability
2nd part) How WW2 made Nazi regime unstable: 1944 total war, mass starvation, 3mn civilian deaths etc.; loss of support for Nazi regime by end of war as Germany began to lose -> in fact can be argued that war was signifcant in causing the Nazi regime to end in 1945, so was far from making it stable
3rd part) Managed to have time to compare it to other factors in making the regime stable: 1) propaganda e.g. Goebells, KdF, SdA etc. -> stability as people were brought around to supporting the Nazis, 2) control e.g. SS, Gestapo, conc. camps, Blockweiters etc., people were forced to support the Nazis so it was stable
Conclusion: WW2 was not at all significant in ensuring Nazi regime's stability; in fact vastly weakened it and led to its demise.
I agree that the Grade Boundaries may be slightly higher than usual this year (after relatively easy Paper 1 and Paper 2), but I wouldn't have thought by too much as remember that everyone doing all the different topics gets the same grade boundaries.