Obj-C download destination + two questions on method names

Hello again,

Three quick questions:

1. To download a file, I use -downloadUrl:overwrite:destination:.

The documentation for the latter says:

"A closure used to compute the destination, given the temporary file location and the response."

What exactly does this mean in practice? More specifically: you set a destination URL using the destination parameter, telling the SDK where you want the file downloaded. Then, the response callback provides the final URL. i.e.:

NSURL *destinationURL = @"/user/username/documents/file.txt";
        DBDownloadUrlTask *downloadTask = [self.dropboxClient.filesRoutes downloadUrl:@"/my/file.txt" overwrite:YES destination:destinationURL];
        [downloadTask response:^(DBFILESMetadata *metaData, DBFILESDownloadError *downloadError, DBError *dbError, NSURL *downloadURL){
            
        }];

So, my question is: in the above snippet, is downloadURL guaranteed to be the same as destinationURL because I set overwrite to YES? I'm assuming (and hoping) that the final file URL of the downloaded file on disk (downloadURL in the above example) will only ever differ from the destination URL passed into -downloadUrl:... (destinationURL in the above example) if overwrite is set to NO. Is that assumption correct?

Then two unimportant questions sprung purely from my curiosity on certain method names:

2. What is the significance of the underscore at the end of DBFILESRoutes's "delete" method? That is, why is it "delete_:" instead of "delete:"?

3. What is the significance of the "d" prefix of all the copy methods - "dcopy" instead of "copy"?

Thanks!

Keith