Impossible 'Delete' scenario?

I have been asked to delete version 5.1 of 3527000.  It has one instance, 3527009 1.8.   Given the 3 delete options,  it seems impossible.

1. Deletes all iterations of the given rev.  Problem is it cant delete the last iteration-total deletion of part-( the instance is rev 1, it would be the last)
2. B.  deletes all revs and iterations – wipes everything  we don’t want that
3.   Delete just the last iteration, but seems how its 5.1, it would be deleting the last REV.  This option  doesn’t allow the last iteration of a rev to be deleted.