To answer your points:
1. Is it required to installed all the components(Management service/distribution/directory) again in the new box?
No just the QVS service would be needed on the new box if you wanted to spread the workload for user requests.
2. I think we have to installed only QV server in the new box
Yes, during the installation you can select to install specific services to install
3. What configuration required to change on QEMC?
You need to add the new QVS to the QEMC, under the System, Setup, QlikView Services option, then the green plus icon on the right of the screen.
4. How it is recognized the other machine?
you would enter the servers name into the above config. the QMC and webserver will then direct traffic to either QVS depending on a number of options that you can set, such as which server has the lower user load and which server has the requested document loaded in RAM already. you can also help to force a user to specific server by setting a document to 'preload' on one specific server if needed.
5. How do you know it is working or not?
You can test by stopping the QVS service on one of the servers, users going to the AccessPoint should then be directed to the available server and you will see increased load on that server.
Also the QEMC should give you a message under the Status, Services menu
6. Our EDX script pointing to server(1) so will it impact anyway if we add one node?
Not too sure, but as the EDX trigger is for a reload this would be talking to the QDS service so should be ok still.
The document 'QV 11 Upgrade and Migration Document' may also help you.
You can also cluster the QDS reload engine to spread the load and provide a backup node, but might need to look into this further in case it requires any additional licence changes.