Event processing after using "virtual" to switch to another virtual server

None of the above. So a couple of points:

1. When you attach multiple iRules to a virtual server, those iRules essentially get compiled together. If each of these iRules have the same events, then those events are also merged - hence the importance of priority ordering. For example:

   iRule 1:

   when HTTP_REQUEST priority 10 {
       log local0. "hello from pri 10"
   }
   

   iRule 2:

   when HTTP_REQUEST priority 5 {
       log local0. "hello from pri 5"
   }
   

   When you add these two rules to a single VIP, you'd basically get this:

   when HTTP_REQUEST {
       log local0. "hello from pri 5"
   
       log local0. "hello from pri 10"
   }
   

2. You can almost think of the virtual command like a pool or node command. While HTTP_REQUEST is triggered when the VIP has consumed all of the request HTTP headers, the virtual command works at a different level of the OSI stack that's targeting a server side resource.

In short, if you have two HTTP_REQUEST iRules on your "external VIP" (with different priorities) and two HTTP_REQUEST iRules on your internal VIP (with different priorities). You can expect all of the external iRules to fire first (in order) and then all of the internal iRules (in order).