Resolved! Create change task when change request is created(Not more than one change task for change request), and in case exiting change request is updated respected change task should get updated.
I have only tried this, (function executeRule(current, previous /*null when async*/ ) { var gr = new GlideRecord("change_task"); gr.initialize(); gr.change_request = current.sys_id; gr.insert(); gs.addInfoMessage(gr.number+"",'Change task has been c...