How to override node clone to its parents node? I am using node clone 7.x-1.0-rc2 module.It is creating clone for a particular node.Now if i published clone.How to override parent node with clone node. Is there any other way or module for doing this?

I am using workbench and my scenario is that i have three types of user contributor,validator and publisher. only contributor can create node and assign it to validator, now here validator can revert to contributor or assign to publisher.Publisher can publish this node or revert to validator.Now i am creating a clone of this node and again send it to contributor and contributor send it to publisher but when publisher wants to publish this clone so old content get update this clone node's content or delete old one and become this node as a parent node.
It looks that you are trying to implement elaborated workflow using node cloning approach.

I strongly suggest you to use Workflow module instead:


  This module allows you to create arbitrary Workflows, and assign them to Entities.
  
  Workflows are made up of workflow states. Transitions between states can be allowed per role. For example, a workflow with the states Draft, Review, and Published could be assigned to the Story node type. Only users with role 'chief editor' can set Stories to the published state.
  You can set up the Workflow to alter states from form, page, comment and a special workflow tab.
  
  Transitions between workflow states can have actions assigned to them. In our example, we could assign an action so that when the story moves from the Draft state to the Review state an email is sent out. Another action could be assigned to the transition from Review to Published so that the node's status is set to Published (and becomes visible on your website).


It is there, it works, and it seems to cover all your needs in one, integrated solution. Even it's example use case is almost exactly like your use case here.

If you want to configure it at revision level more easily, there is also Revisioning, "a module for the configuration of workflows to create, moderate and publish content revisions".


  You use it in scenario's like this:
  
  
  Authors write content that prior to being made publicly visible must be reviewed (and possibly edited) by moderators. Once the moderators have published the content, authors should be prevented from modifying it while “live”, but they should be able to submit new revisions to their moderators.
  We shouldn't have to grant these roles “god-like” powers (e.g. D6's "administer nodes" permission) to implement this.