Round, circular, spherical shapes are the most common in the universe. They are the easiest to form, given all the forces/factors at work, and they are the most dynamic in terms of the use & loss of energy (that is to say that they use very little energy to form and expend very little energy when moving).
Take the shape of a raindrop as an example. We all think it's tear shaped, but a raindrop is actually a perfect sphere as it fall's from the sky because of all the forces and pressures at work and how easy that sphere shape is to form.
It would be impossible for the raindrop, or a planet (or even a planets orbit for that matter), or the galaxy we're a part of to move in a square or triangular or hexagonal or trepezium shape.
As for "stardust evolving" into a living thing, it's not "stardust", it's a collection of atoms & molecules which, when put together in various quantities form "stardust", gases, planets and everything in our universe, including all living things.
Finally, can we call stardust a living thing? Well, can we call the Earth a living thing? It move's, it breathes, it reacts when we hurt it, just as we do when something on our skin causes us a discomfort. I think the answer to your question is a quite simple yes. The entire universe is a living entity, it's not just us.