Can Apple Card be used as a credit card in stores

Yes. The Apple Card is a Mastercard credit card. If the store accepts Apple Pay you can charge your Apple Card using that. If they don't accept Apple Pay, you can use a physical (titanium) Apple Card. See: How to request or replace a titanium Apple Card - Apple Support

Also see: How to make purchases with Apple Card - Apple Support

Are you referring to Apple Card Mastercard (credit card) or Apple Gift card? Those are two very different financial instruments.