How to access the USB device?

I want to access files that are inside a device with MFi authentication. After researching on the Internet, I found that it is possible to access it by providing the UI Supported UIExternalAccessoryProtocols key from Apple. Please let me check a few things

  1. Please tell me how to provide the key
  2. After getting the key, do I need any API to access the device with MFi authentication?
How to access the USB device?
 
 
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