DasCodes

There are many plugins for rating and related post available in plugin directory.

You have gone far. Try adding an image in featured section of the post/page (Theme must support featured option).

I would rather say not to give access to database to public. BTW you can use WooCommerce plugin for maintaining products.

Buddypress can be used as forum. Don’t know whether Buddypress can manage various user roles, haven’t gone enough with it. You can use s2Member plugin for dividing user roles. You can add a section for choosing roles while registering with s2Member. It supports custom register page.