There are no upgrades that change the fact that a free hosted WordPress.com blog is still subject to the same limitations and restrictions. When you purcahse a domain and domain mapping that’s what you get and nothing more than that.
See here: Important Notes Before Upgrading
If you require FTP access and plugins and advertising then you need to hire a web hoste and set up a self hosted WordPress.ORG install.
See here for all the differences: WordPress.com vs. WordPress.org