If it’s an Azerty-keyboard, I’m pretty sure it’s not an original Chuwi since they only make International Qwerty models AFAIK. Are you sure your keyboard has a back-light?
To get in the BIOS it should be the ESC-key regardless of Azerty or Qwerty lay-out.
As for the SATAIII-mode, there’s a topic on this very forum for that already 