PRASANTH, the above share link contains the sample configuration screen shots for your reference. In your case you need to go to Designer Studio > Org & Security > Access Manager and configure the FULL ACCESS to Open and Perform to the Manager and NO ACCESS to your end user, so that manager will have the access and end user will be restricted. Hope this might help you to achieve your requirement.
Then you can try with the pyStartCase flow, where you can try to define the Start conditions and Security to define privilege as explained by Govardhan in the last comment of this post and see if it works.
PRASANTH - i had tried to implement your requirement with a sample use case and you can have a look into my attachment, so that it can be helpful for you to implement your exact requirement of restriction.