I want to overcloak my i5 6500 but i need to update BIOS for that. I downloaded Overcloaking BIOS to USB stick and tried to update it with Q Flash but it says "No device found".
Which motherboard and BIOS are you trying to use? The i5 6500 is a locked CPU, and will require BCLK adjustments for OC if BIOS supports it. I believe only ASRock boards had this option for a limited time before being locked out again.