Custom Builds

if you can access all the CSS, JSON and HTML in the Developer Platform can just delete the Square Space Template code and build what ever you want to build?

For clarification. The Developer Mode is for v7.0 sites only.

I don't know if I'd go as far as to say you can build whatever you want. You do have much more flexibility with DM but you are still restricted to the box that SS provides.

Unlike if you were to buy your own servers and software and build your own stack.