Finally i found the solution for this . I am giving solution here so that it may be helpful to others who may face difficulties like me,
After changing context root just start your deployed war file and Test it .
While reaching URL,
Web page will display showing "apex listener not configured" and it will show you configuration location on webpage itself .
So you just copy all the directories and sub-directories( which got created when you configured your database using war file) to the location which shown on webpage.
Since we change context root so a context root named directory use to get create inside configured path, so web is unable to find configurations because it gets store inside different directory so just copy all and try . It worked for me very smoothly .
My location was "/home/oracle/apex_listener.18.104.22.168.10.13/apex" (Before changing context root in weblogic server)
Then after changing and starting the deployment again, it became "/home/oracle/apex_listener.22.214.171.124.10.13/dev" , since i given my context root as "dev".
And all applications working fine too .
Still i felt as its not correct way of doing in security point of view but its the solution i found and i will try apache to redirect my URL .