I would consider myself a full stack developer, hell I've even made a decent career out of it. I don't have a CS degree, what I do have is many many years experience. I know HTML, CSS, JavaScript (including whatever the latest fad is be in jQuery, Node, Ember et al...), PHP, Python, Java, SQL (MySQL and MSSQL), NoSQL (Mongo, Elasticsearch etc...), and I can set up, secure and maintain a web server running Ubuntu, Redhat or CentOS.

You can't reliably learn all of this from an online course, although it might be a good starting point, you become a good full stack developer after years of experience.