Final answer:
1) Tapestry needle. The most appropriate hand needle to use for repairing and installing a seat cushion cover is a Tapestry needle.
Step-by-step explanation:
The most appropriate hand needle to use when repairing and installing a seat cushion cover is the Tapestry needle. Tapestry needles have a blunt tip, which makes them ideal for working with thicker fabrics like seat cushion covers. They also have a large eye that can accommodate thicker threads or yarns used for stitching the cover.
The other needle options - Crewel needle, Sharps needle, and Embroidery needle - are typically used for other types of embroidery projects that involve finer fabrics or detailed stitching.