Samsung - Galaxy S4 Mini (International LTE) - serranoltexx - Documentation Suggestions

Windows and Heimdall together may not be the best approach (loosely speaking the Linux Heimdall product has been adjusted to work with most Windows) Windows has the product Odin.

I would check out this approach

… or use a Linux PC

ERROR: Failed to access device. libusb error: -12

is itself a Linux error which “should not happen” (but might !) in up to date Linux, but I could not point to a fix in Windows.