Can I use the prepared USB from a failed partition Boot Camp
Generally, the following applies.


The 2011 and earlier Macs use both a DVD and flash drive to install
Windows. The DVD contains Windows and the flash drive contains the
Boot Camp Support Software. Apple does not officially support Windows
10 on these models, but Windows 10 can be installed on most of these models using the legacy BIOS boot method. You should then install the
latest Boot Camp Support Software available for your model Mac.
The 2012 through 2014 Macs use a flash drive to install Windows. The
the flash drive contains both Windows and the Boot Camp Support
Software. The Boot Camp Assistant should be used to create the flash
drive. Windows 10 is installed on these models using the EFI boot
method.
For the 2015 and later Mac models, the Boot Camp Assistant installs
Windows 10 directly from the Windows 10 iso file. So there is not
need for either a DVD or flash drive. Windows 10 is installed on
these models using the EFI boot method.


When installing Windows, there is no need to partition the drive. This is done by the Boot Camp Assistant before the Windows installer starts. However, you do need to format the partition where Windows is to be installed. You need to tell the Windows installer to preform this task. So when you see the window shown below, you should select "Custom: Install Windows only (advanced)". Next, select the Boot Camp partition, then click on the "Format" button.