Full stack development doesn't mean that you work on all the things in the world, just all the things in your stack. You would work on the HTML/Javascript/CSS, the middle layer (PHP, Python, Scala or other), and the database. If you find a way to competently work on all those things, BOOM, you're a full stack developer.
The secret to doing full stack development well is figuring out how to keep the number of things you need to know at any given time low. A product that is using Ember, React, Angular, PHP, Python, Scala, Postgres, Redis and MongoDB is going to be hell on the developers. The developers (and the product) would likely benefit from some serious triage work. Get rid of half your middle languages and half your databases, because they are redundant and doing so will make your life easier. Great engineering depends very much on deciding what you can get rid of.
How this relates to freelance work, I couldn't tell ya. By hopping from project to project it seems like you're going to be exposed to a mind numbing number of technologies. Sounds like fun actually, but it's a different animal from full-stack development. Most of the successful freelancers I've met focus on a particular technology. E.g. Mongo contracts out experts in their database, some people specialize in search technology, others do HBase. Nobody does all of those things at the same time.
The secret to doing full stack development well is figuring out how to keep the number of things you need to know at any given time low. A product that is using Ember, React, Angular, PHP, Python, Scala, Postgres, Redis and MongoDB is going to be hell on the developers. The developers (and the product) would likely benefit from some serious triage work. Get rid of half your middle languages and half your databases, because they are redundant and doing so will make your life easier. Great engineering depends very much on deciding what you can get rid of.
How this relates to freelance work, I couldn't tell ya. By hopping from project to project it seems like you're going to be exposed to a mind numbing number of technologies. Sounds like fun actually, but it's a different animal from full-stack development. Most of the successful freelancers I've met focus on a particular technology. E.g. Mongo contracts out experts in their database, some people specialize in search technology, others do HBase. Nobody does all of those things at the same time.