GameJolt is full of free Sonic fan games. Some developers name their projects misleadingly to attract searches. Examples include:

Because the portable version doesn’t check for file integrity, you can stack dozens of mods without Steam redownloading vanilla files.

Because the portable version is already cracked and decoupled from Steam’s DRM, applying mods (like the infamous Sonic Generations Overclocked or Unleashed Project) is often easier. You don’t need to disable Steam auto-updates or fiddle with API wrappers.

With these settings, even an Intel Celeron laptop from 2015 can hit 720p at 30–40 FPS.

There is no official "Portable Edition" released by SEGA. However, you can create one legally using legal tools if you own the Steam version.

How to create a portable version (Legal Method):