Border between Hungary and Croatia was defined along the rivers of Drava and Danube. In medieval times, although Croatia in theory, Srijem was governed by Hungary. After we defeated the Turks the border went along the rivers with Petrovaradin and Zemun in Croatia-Slavonia, although it was governed directly by the Austrian army until the disolution of the military border. 1699.-1918.
Kotor was mostly an independent Dalmatian comune, at times vassal of Byzantium, Venice or the Kingdom of Hungary, Croatia, Slavonia and Dalmatia. As it is south of Drava and falls under the Triune Kingdom of Croatia, Slavonia and Dalmatia. Later, after Napoleon, it became part of Dalmatia, although it was governed as a crown land of Austria, it was still part of Dalmatia, one of Croat kingdoms. And Kotor was not in NDH, it went to Italy. And if you want ancient history, it was part of Red Croatia in 8th century.
As for Mostar, for most medieval period southern Croatian border went along the river Neretva, that would put the location where Mostar would be founded later into Croatia, earlier settlments existed at that location. After we revolted against the Turks and liberated Bosnia it was first under Austrian occupation, then after annexation of Bosnia it remained in a limbo between the two parts of the monarchy. While it was never part of Croatia proper, it was part of a Croat state. Since it it a mostly Croat town the logic to include it is similar to the logic to include Banja Luka as a Serbian town, with the exception that Mostar region was part of Croatia while Banja Luka region was never part of Serbia.
Trieste... Trieste is ours! At least until the Allies forced us out in June '45. J/K
As for the NDH period, I dont bother with it, since it was not a Croat state, but a Nazi puppet state.