Did any of the participants in the war, have any demands prepared before the war started or were these demands prepared during or at the almost end of WW1?
This goes for both, the Entente and the Mittelmächte. My main interest here lies with the Mittelmächte though, as they do not seem to be discussed as often.
Most demands for peace treatises were formulated after the outbreak of hostilities; a good example from the Central Powers would be Bethmann-Hollweg's September Programme of 1914, which laid out some of the aims of the Kaiser Reich. Fritz Fischer's German War Aims is the classic study for this case, and others like it. David Stevenson surveys the war aims of both sides in 1914-1918.