Where does LLMs fail the most?

I wonder to know how and what should I ask to the LLMs and what should I never ask them.

I know I can't ask for complex mathematical question. But lately, 5 minutes ago, I asked ChatGPT the following: "At a low level, how does a controller (HID controller) communicate via Bluetooth to both send keystrokes and receive vibrations?"
And answered me in a line the following: "Example of an input HID report in binary format"
But the format was in hexadecimal, not binary: "0x01 0x80 0x00 0x7F 0x7F 0x00 0x00 0x00"

I know this because I studied ICT, but, what If I didn't? How can I be sure that info told by LLM is veridic?

Hope you guys can understand my English level.