Hii Ramesh,
For approval of notification at different levels you can go for user status for notification by following the below path
SPRO --> Plant maintenance and Customer Service --> Maintenance and Service Processing --> Maintenance and Service Notifications --> Notification Processing --> User status for Notifications --> Define Status Profile
Here first define user status profile in "Define User Status Profile for Notifications" and then assign the profile to notification types in "Assign User Status to Notification Types"
For detail explanation of user status refer User Status in SAP.
Hope this solves your problem.
Regards,
Shiv