To your bonus question, the wheels being faceted is due to the model being too low-poly. You could probably solve that pretty easily by putting them in a Subdivision Surface object, but you’ll need to add some loop cuts around the edges to keep them intact. Or you could just replace them with a tube primitive. The edges on the cannon are a shading issue probably due to phong issues. You might try optimizing the model. If there’s a normal tag on it, removing it might help.
In fact, if there’s a normal tag, removing it might solve the reflection issue too.
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