Add more than 5 sandbox solution web parts to a single page

sorry Bhuvanesh but what you said thats not clear to me,the web part i am creating that is very simple just print hello message,and as i know ,there is no any property like maximum allowed range as[5]for web part at visual studio,right??the issue i am getting thts the behaviour of sharepoint online,where you are getting that error message when u are trying to add more than 5 web parts on same page.

Check for the properties of the solution or any configuration data hold the maximum allowed range as [5], do an search for 5 and try to edit to 6.