Getfolderitem Volume(i).name error (":" replaced by "/")

No.

There is a difference between a WINDOWname and a FILEname.

After all the Finder is just another app, and what you see is how the finder shows you the underlying file information.

Accessing that file information is a different cattle of fish.

It is the same in your apps: a document shown in a window has a Title, but the file name is not necessarily the same.

And there is a good reason for that.

Read up on file delimiter in the folderitem documentation.