2) If we have two managed servers, do we have to deploy same ear,war,jars to both servers?
I believe yes. If you want a ear/war/jar to be deployed on more than one servers, you need to deploy it on all of those servers. However, while deploying the application, you can select multiple target servers. By doing this the app will be deployed on all the selected target servers in one go.
3) Do managed servers run on different ports ?
Yes, different managed servers has to run on different ports.