Usually this is because the view vector is defined by the position of the mesh, but you're trying to use it before the position of the mesh has been defined. You can probably construct your own view vector though, using normalize( cameraPos - worldPos ), although I'm not sure if you can use worldPos for that

Not sure if I understand you fully, but, this is likely because on the nodes themselves, you only see a single light source, while in the preview window or in-game, you'll see all lights affecting the object

This might help:

https://twitter.com/JoachimHolmer/status/657436624498880512

https://twitter.com/JoachimHolmer/status/730521542254174208

Originally from this talk from Alex Vlachos:
http://www.gdcvault.com/play/1021771/Advanced-VR (The section on geometric specular aliasing)

A halfway solution that skips the manual editing is to use the append node to append the float to itself three times, before going into the lerp node.

Multiply it by the normal direction

Currently it's not planned. Also, this has been requested before, closing thread!

You'll need to rename the second one

Shader Forge doesn't support vertex lit yet I'm afraid