Per the manufacturer, the Seresto Cat Flea and Tick Collar does not expire as long as it has remained in its original container and stored in room temperature conditions.
The Seresto Cat Flea and Tick Collar will kill fleas. It does not repel them. It works similarly to a monthly topical, but as the active ingredients wear off over time, a new supply is continuously replenished in low concentrations. The active ingredients spread from the site of direct contact over the skin surface.
No, the Seresto Cat Flea and Tick Collar can only be used on cats.