Sure it wouldn't look the same in the sky or through a telescope but it WILL cast light in the same manner as a spotlight.
Let's stay on topic and address one item at a time, the OP has asked a specific question about the direction in which light travels.
In that case, I request evidence for your claim: "the source light being any shape, will still cast light upon the earth in the same manner as a spot light would."
I can imagine many geometries for the Sun that would not cast light upon the Earth in the same manner as a spotlight. One, for example, would be if the Sun was shaped like a long, thin tube. Another would be a torus. In fact, there are quite few geometries that WOULD work. And it would certainly matter if the light was uni- or omni-directional. Simply take a flashlight, and put in front of it a piece of paper with some shape cut out of it -- so that the light only shines through the shape's hole in the paper. Now shine it on the table. Obviously, the shape of light it makes on the table will vary dependent on the shape cut out of the paper.
Hence, I have direct, observational evidence that contradicts your claim. Ironically, playing with scissors and paper and flashlights is something one might do in grade school -- so your earlier suggestion for another member to go back there was a good one!