Apple itself does not and never has sold refurbished iPhones. Nor do any Apple Authorized resellers sell Apple refurbished iPhones (they may sell iphones refurbished by themselves or a third party, but not Apple). Any refurbished iPhone you purchase is under whatever warranty is offered by whomever refurbished it (Amazon or some third party refurbisher/reseller). Apple sells only retail new iPhones, with a one year warranty restricted to the country of original purchase.
So anything you buy "refurbished" is just another used device as far as Apple is concerned, and if it is one actually opened up and worked on by a third party, any and all Apple warranty is then voided.