Most likely, yes. As long as the cross appears 'golden' (that is, either of yellow metal or gilded) and, of course, hasn't been altered by greedy 'traders' later on, it would be the top two classes.
No, that is incorrect. Until [at least] the end of the war, there were 3 classes of the soldiers' cross. However, we can be fairly certain that there were no wartime decorations, per se. In December 1885, once the war had ended, a fourth class is added. And no, the folding of the ribbon had little significance and cannot be used to date crosses - we can see pentagonal ribbons from the Balkan wars, as well. The folding of the ribbon was just a preference of the bearer, ribbon manufacturer specifics (to an extent) and partially a heritage from the Russian influence in the Bulgarian military.
Yes, it's possible.
We do not have sufficient information to speculate about the country of origin.
If you are interested in the historical aspects of the topic, I would encourage you to search for Todor Petrov's book "Наградната система на България (1878 - 2010 г.)". It's a very good source of information, giving a clearer historical context, especially for those initial stages of the award system.