Tape access sis strictly sequential. One file after another, but they are not different "files" on tape, they are one file in MTF (MicrosoftTapeFormat). Restore software reads the single big file and selects the data corresponding to one logical file based on "marks" in the bkf file
I'm not sure where you are trying to go here. You cannot delete only one "file" from a tape or insert a file. You can only delete the entire BackupSet or append to the end of it.