How to change the username label for a guest user

You may use this CSS code below to change Username label to say “Full Name” when logging in as a guest.

.guest-login-dialog [for="guest-username"].login-label.cell {
    color: transparent !important;
    position: relative;
}

.guest-login-dialog [for="guest-username"].login-label.cell::after {
    content: "Full Name";
    color: #666;
    position: absolute;
    left: 0;
}