Yola asked: Do the borders have to be cross stitched or can another stitch be used; for example a Smyrna stitch?

A: Borders provide an opportunity for individual expression. So long as you observe the guidelines for borders regarding colours, size, positioning; and your embroidery does not distort the surface or tension of the aida cloth, other stitches may be used.
See the BORDERS ALERT! page in the Design and Technique section.