No, you cannot use a phone as a bootable USB. A bootable USB is a storage device that has software installed on it that allows a computer to start up or boot from it, which is used to install an operating system, run diagnostics, or recover data. A phone, however, does not have the necessary software or hardware components to act as a bootable USB device. While you can use a phone to transfer files to a computer, it cannot function as a bootable USB. If you need a bootable USB device, you will need a USB flash drive or another bootable device that is designed for that purpose.