I didn't know you could play any part of the game on an Android device.
I just know that for the computer, you'd unzip the file and you will have a 'samorost' folder; open that folder and then open the main.swf file using Flash Player. You don't need to do anything with the .swf files; just leave them all in the 'samorost' folder.
Not sure what you mean that this "happens only when the file is incomplete". By "file" do you mean "folder"? Are you taking one of the .swf files out of the 'samorost' folder? If you are, then yes, there will be a black screen once you get to the corresponding level.