Hi Narendar,
1) When we have to stop/disable Original APS, after enabling newly create servers and testing them or before enabling them. - Yes, you must stop/disable the original APS before starting up other cloned APS services. I would suggest creating all of the APS services, shutting down/disabling the original APS, and then start up all of the cloned APS services.
2) Do we have to stop cloned APS also as there will be dedicated servers for each service? - Not sure I understand this question. If you have an original APS and a cloned one, the one you don't wish to use must be stopped/disabled.
3) Need more information on Promotion Managment Override settings and Manage Systems. - JRK provided a perfect link for that, I'll defer you to his post.
4) If I start the SIA, will dedicated servers will be started automatically ? - If you don't uncheck the box next to 'Automatically start this server when the Server Intelligence Agent starts', the servers will automatically start back up. Uncheck these boxes for the services that you stopped/disabled.
Let us know if you have any other questions/concerns. Thanks,
-Victor