Presently, I configured a deployment server - the deploymentclient.conf is present on each server - Should be possible to update the input.conf file content - like a new index name or a new eventid in the white list using the deployment server?
Yes, that is the whole point.
I think you will want to review the deployment server documentation.
If you bundle your inputs.conf in an app, deployment server is the mechanism to distribute that app out to the forwarders based on the serverclass.conf settings on the DS.
deploymentclient.conf is the forwarder-side config file.
Settings that are made outside of ../splunkforwarder/etc/apps are not manageable using the DS.