All fields can be deleted but when it’s “hardlocked” then you should also change your template files manually (this is why it was hardlocked).
My suggestion is if you don’t like it to rename or change it, and not remove this locked fields.
If you really want to unlock those items, you need to know what you are doing, here is instructions:
Run this SQL query on your database via PhpMyadmin for example:
UPDATE `option` SET is_hardlocked=0