For k2 user module, after the user successfully created an account, the display message is on the bottom, user has to move the page to find out if it's successful or not, can we have the displayed message displayed on the top, so user doesn't have to move the page to see the result.

Hi. First, the message is not placed by K2, it is placed by Joomla! users extension. Second, the place that system messages are printed has to do with your template, not the extensions. If you want to change the message position you need to update your template's code. If you do not know how to do this ask your template provider for help.