In AEM 6.4, when i am trying to resize the components in layout mode, it's not working for mobile and tablet layout.
It's getting resized in Desktop layout but not in mobile. Can anyone please help with this issue.
Have you added the required CSS to do so? Follow the WKDN tutorial and you will get the CSS that lets you adjust the layout.
Last time i worked with that - the layout for mobile was working. Download Section 6 from Github and look at the layout there. It works nicely: