I'm trying to develope a few components using AEM 6.4 version ( more features with respect to previous versions ) and I'd like to use and deploy a such components ( say aAem contents ) on AEM 6.0 Publish Instance since in our server it is the Aem that is running.
Why do you update only the author and not the publish instances?
To answer your question: It's not supported. It might work, but with some high probability you might run into issues you cannot resolve easily, and also support won't be able to help you. Not to mention issues you'll already have at deployment time (e.g. bundles with non-resolved dependencies).