How to force Gigabyte motherboard to boot in the backup bios by shorting pins on the bios chip?

You said that you had problems with your old BIOS, but then you flashed a new BIOS. It sounds like you have a corrupted BIOS, and that is why you are asking to boot back into the backup BIOS.

Anyway, here is how you boot back into the backup BIOS:

Method 1

1. Shut off your computer
   
2. Hold the power button until your computer starts and shuts down again
   
3. Press the power button again, your backup BIOS should kick in now and should re-flash the backup BIOS if there's anything wrong with the new one.

Method 2

1. Shut off your computer
   
2. Hold the power AND the reset button for about 10 sec, than release.
   
3. It should boot into the backup BIOS now.

Method 3
Only use this if nothing else works.

1. Short out pins 1 and 6 on the main BIOS chip by attaching a jumper to both the pins (pin #1 should be marked with a red dot or whatever)
   
2. Tell a friend to press the power on button while you do this because right now you are holding the jumper on the pins
   
3. Remove the jumper you're holding between pins 1 and 6 as soon as you hear a beep.
   
4. Backup BIOS should boot now.