How to add Routings in Service Operations?

Dear All,

Here I have observed that whenever we are going to use the service operations there are so many routings are already attached to them. Here my first question is that why they are attached by Default?

Another Question that, we have created one routing for every service operation now we want to attach it with the service operations but there is no option to attach a new existing routing, so from where we can attach Routing to Service Operation?

Third Question that, is there any option by which we can disable all the routings in one Go and active our our created Routing to every Service Operation in one Go?