it shows the function related to root url i.e. ('/') but if i write @app.route('/home') it gives me that error
Based on your clarifying comments, it appears your browser is accessing a previous version of your app server.
I have run into this problem myself when using the PyCharm IDE. On Windows, the way to shut down these old versions of the server is to press either Ctrl+Alt+Delete or Ctrl+Shift+Esc (Windows 10) to view your list of running processes. Then scroll down until you see processes named Python and shut them all down.