In the documentation, under this path:
Doc 1. CryENGINE Free>
CryENGINE Directory Structure
This is written:
The main solution of the engine is Code/Solutions/CryEngine.sln or Code/Solutions/CryEngineGfx.sln, depending on whether you have an SDK with support for Scaleform or not.
Does the Free SDK include Scaleform support?
If so, I can't find the CryEngineGfx.sln file.