For testing purposes, I had done some core changes to the following files and they worked fine.
So after my test, I replaced back the original with the revised files. After going through Cache Storage Management, and flushing all, I am still seeing all of my revision in place!
While looking through FileZilla at var/cache/ and it's sub-folders, flushing cache on the Back-end does NOT delete all cache in mage--0, mage--1, ... and mage--f.
I have to keep on pressing "Flush Cache Storage" to delete all. How can you delete all cache at once? And even after emptying the folders, the changes do not roll back!
What else can I do to roll back to original, even though I have both original file in place?