For USB key function, please download F-Stream Tuning Utility ver:2.0.11 from below link and then install it to try.
Link: ASRock > Fatal1ty Z87 Professional
After installing it, you can see USB key in option.
Please plug a USB drive and then key in "your password" to use this function.
If any question, please feel free to let me know.
Thank you very much!
Have a nice day