Trying to restore iPhone 8 Plus

Hello!! I am trying to give my little sister my old Iphone 8+ but it has been disabled, i have tried to restore it through itunes but cannot log in to my old Apple ID due not having access to my old phone to get the two-step authentication code. i have also tried to factory reset the device using the buttons but is also not working.... is there any other way i can possibly reset the phone, or get the two-step code changed to my email connected to the apple ID or to my new phone number? Thank you

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