You asked: 'And what does /opt/apps/kitchensink mean in this context? i.e., are we talking about a file from the application's Resources directory?' -- It means any physical file system path. The file can be from application's Resources directory, or from any other location (with respect to file permissions).

You asked: 'And by the way--can you open a file from the resources directory using Ti.Filesystem.File on Tizen?' - No, you can not.