Summary: These functions add, delete or update the given blog_option, respectively.
Detail: All three of these functions use the switch_to_blog() function to navigate to the selected blog and switch it’s option values. In fact, they’re all pretty good examples of how that function can be used to toggle between blogs. Apart from the fact that one deletes and the other two set a variable, there really sn’t much difference between the functions. All set their updated values to the wp-cache.