1> 1st task created2> when 1st task closed then 2nd task and change request will be created3> 3rd task created when <2> 2nd task and change request closed (When change request closed, automatically 2nd task should be closed) then 3rd task will be created.

If anybody tried to close 2nd task before closure of change request then error should pop up(Task will be closed automatically when change request closed, please close the change request which is related to current request).