I'm studying now about projections with OpenGL and I've some questions:

Is there importance for the viewer's location? I know if I move forward/backward it won't mind, but what if I move upward with 30 degrees for e.g.

Does the viewer is located in the 0,0,0 axis? or he can be in another place after defining glOrtho's properties.

Are there only 6 projections? (I'm asking this because of the properties of the box, and defining the glOrtho - near, far, left, right, up, bottom)

Can I hide objects with ortho proj? I think it's obvious that yes, but I'm still curious maybe I'm wrong.

Do objects that are closer to me seem bigger, meaning that other objects may be hidden? I believe that not. the objects don't seem bigger. they stay the same size.