How to Sell Out of Stock Product on POS but Can not Sell on Website

If you want to sell out of stock product on POS, without selling on the website. Please go to Backend > POS > Settings > Checkout section and select setting Add out-of-stock product to cart is YES

If you don’t want to sell out of stock product on Website, please go to Store > Configuration > Catalog > Inventory > Product Stock Options and choose the setting Backorders is No backorder