That model runs Embedded Gaia which is not the same as regular Gaia.
Also, you are limited to R77.20.80 which is the last release supported on that model.
If it's actually an SG80 then you're stuck on R75.20.
If you want to learn about Gaia, you're better off downloading R80.40 and installing in a VM.
Or better yet, check out our new CheckMates Labs, where you can play with pre-configured environments:
https://community.checkpoint.com/t5/CheckMates-Labs/bg-p/CheckMatesLabsRight now, we only have one lab posted but are expecting to make more available in the near future.