1. I’m afraid there’s an error in the documentation. GazeAware component only works for 3D objects. For 2d objects you might need to do bounds check manually. So just read your canvas element bounds in Screen coordinates add a margin and compare it with gaze point coordinates. You might also want to add some stickiness or your selection might jump between several objects.
2. Unity SDK is the only SDK compatible with Unity.
3. We will soon release a major update for the Unity SDK with an example for CleanUI feature that does the bounds check you need.