The coronal suture is located in the skull. It connects the frontal bone to the parietal bones. If you take your fingers and point to the outside corners of your eyes and then move them straight up, it's roughly positioned there, across the top of your head.

Squamous suture (separates the temporal bone from the parietal bone), Coronal suture (separates the frontal bone from the parietal bone), Sagittal suture (separates the parietal bones) and the Lamboid suture (separates the occipital bone from the parietal bone)

By the 6th year.

No, the parietal and frontal bones are joined by the coronal suture. The saggital suture joins the parietal bones to each other.