You’d attach the sleeve as you would normally with the piping cord part on the garment side of the seam allowance. A piping or cording foot works fantastically here! But a zipper foot works just as well. Put the zip foot on so it sits on the “right” of the seam line, on the seam allowance. Sew the sleeve in with stitches right next to the piping (which, again, is on the garment side, or to the left of the zip foot and seam line). If in doubt, pin in the sleeve then hand baste loosely around the seam line to get the idea of where all the layers (including piping) are laying in the seam before final stitching. Good luck!

Yes, you’ll need to apply the velvet pieces by hand. Needling turning the raw edge under is the best way to go. You could also test a Fray-Chek type of product to “seal” the edges to help prevent fraying as you applique the pieces.

Thank you
Lettitia