Stuck in penumbra demo

[Yuhaney]

is the demo different than the tech demo? the one I played sounds like the one he is talking about, down the cave, dog to the right, and it ends.
If they are different, is the other available for linux? I guess it doesn't matter unless the tech was different than the full version, like different area, or different beasts, story, something

Yes. They are different. But it's not available for Linux, only Windows.
But if you have Windows you can download the 2006 Tech-Demo from the following link:

Penumbra Tech Demo Download