The Germans were to blame
Serbia
Germany was forced to take all the blame for World War I as dictated in the Treaty of Versailles.
Germany
Yes
Yes
France
The war guilt clause forced Germany to take all the blame for World War I.
Japan
It depends on which war. If you are asking about World War 1, I would say no. I think Austria-Hungary should get most of the blame. In World War 2, I would say Germany was to blame, but I will also add that other countries were headed for war anyway regardless of anything that Germany did.
Germany
Japan, too.