The glitching of the terrain is something that I noticed happens a lot on the OpenGL version of the game. On the Windows version it is not that bad. I have no idea how to fix this and this is far from the only issue I had while using the Unity Terrain. The lighting issue is mainly down to the materials/shaders I used as they don't show you where shadows are so when you enter one it only affects the plane. The view distance is intentionally turned a bit down, as I wasn't sure how performance intensive Unity Terrain are. I was planning on adding a setting for this, but I didn't have time.
I am not sure what happened with the text on your screen. I configured the Canvas for 1920x1080 so your resolution might not be the same.
I am sorry I delivered something so glitchy but I started work on Friday and I really wanted to finish this game idea that I had.