According to the standard Android documentation, the prefered way to start a service (started service that is) is to use an explicit intent like this:
// Using e
A1 : Even though your activity and service run in different processes they still belong to same Application. You can still use explicit intent, I don't see any specific advantage of using implicit intent here (let me know if find any :) )
A2 : let me list down few facts here
Now to answer your question, if you service is still running (because of startService() call by previous activity), then bindService()/startService() will make sure to connect to existing service.
Hope this is of some help to you. Let me know if you have any other specific questions.