Thank you @Ravenmaster. 

Thank you @yurasicpark74 and @0mnious for your reply. My usb is 32GB and formatted in FAT32 and also in MBR partition. 
 
A new development for this issue : After the tech support respond to the POST LED 1.5 issue, I have installed all other components i.e CPU (13900K), GPU (RTX 3090), RAM, SSD. When I boot up the system, and presss DEL, there is nothing show on the display, the POST LED in the 00 54 7F 59 loop. So, I took out all the power cable from the PSU except the 24 pin (as I do not want to take out all other installed components), and do the flash bios by following the "Update BIOS without CPU" procedure, with the same usb drive, this time I can see the circle flashing on the POST LED, my happiness end when I see the code E3 on the POST LED. What should I do now ? To uninstall all the components and do the flash again ? Or I can use other version (the version on the usb is 2.03) to update without uninstall components but take out all power cable except 24pin ? Or I should let all power cable connected and do the flash bios again ?
 

Did you try to do the pre-boot flash with everything installed?

Also, do you have an old 1-4 GB (or even smaller) USB stick you can try?

kk700
Thank you @yurasicpark74 and @0mnious for your reply. My usb is 32GB and formatted in FAT32 and also in MBR partition. 
 
A new development for this issue : After the tech support respond to the POST LED 1.5 issue, I have installed all other components i.e CPU (13900K), GPU (RTX 3090), RAM, SSD. When I boot up the system, and presss DEL, there is nothing show on the display, the POST LED in the 00 54 7F 59 loop. So, I took out all the power cable from the PSU except the 24 pin (as I do not want to take out all other installed components), and do the flash bios by following the "Update BIOS without CPU" procedure, with the same usb drive, this time I can see the circle flashing on the POST LED, my happiness end when I see the code E3 on the POST LED. What should I do now ? To uninstall all the components and do the flash again ? Or I can use other version (the version on the usb is 2.03) to update without uninstall components but take out all power cable except 24pin ? Or I should let all power cable connected and do the flash bios again ?
 

You need a flash drive with a maximum size of 4 GB. 32 GB is not suitable for flashing. First, find the flash drive. Then download the bios from the site. Rename the downloaded file to EVGAE699.bin and put it on a flash drive. And then everything according to the instructions.

yurasicpark74

kk700
Thank you @yurasicpark74 and @0mnious for your reply. My usb is 32GB and formatted in FAT32 and also in MBR partition. 
 
A new development for this issue : After the tech support respond to the POST LED 1.5 issue, I have installed all other components i.e CPU (13900K), GPU (RTX 3090), RAM, SSD. When I boot up the system, and presss DEL, there is nothing show on the display, the POST LED in the 00 54 7F 59 loop. So, I took out all the power cable from the PSU except the 24 pin (as I do not want to take out all other installed components), and do the flash bios by following the "Update BIOS without CPU" procedure, with the same usb drive, this time I can see the circle flashing on the POST LED, my happiness end when I see the code E3 on the POST LED. What should I do now ? To uninstall all the components and do the flash again ? Or I can use other version (the version on the usb is 2.03) to update without uninstall components but take out all power cable except 24pin ? Or I should let all power cable connected and do the flash bios again ?
 

You need a flash drive with a maximum size of 4 GB. 32 GB is not suitable for flashing. First, find the flash drive. Then download the bios from the site. Rename the downloaded file to EVGAE699.bin and put it on a flash drive. And then everything according to the instructions.

Thank you @yurasicpark74, I have followed your suggestion, but I can only find an 8GB usb. Anyway, it works. 

kk700

yurasicpark74

kk700
Thank you @yurasicpark74 and @0mnious for your reply. My usb is 32GB and formatted in FAT32 and also in MBR partition. 
 
A new development for this issue : After the tech support respond to the POST LED 1.5 issue, I have installed all other components i.e CPU (13900K), GPU (RTX 3090), RAM, SSD. When I boot up the system, and presss DEL, there is nothing show on the display, the POST LED in the 00 54 7F 59 loop. So, I took out all the power cable from the PSU except the 24 pin (as I do not want to take out all other installed components), and do the flash bios by following the "Update BIOS without CPU" procedure, with the same usb drive, this time I can see the circle flashing on the POST LED, my happiness end when I see the code E3 on the POST LED. What should I do now ? To uninstall all the components and do the flash again ? Or I can use other version (the version on the usb is 2.03) to update without uninstall components but take out all power cable except 24pin ? Or I should let all power cable connected and do the flash bios again ?
 

You need a flash drive with a maximum size of 4 GB. 32 GB is not suitable for flashing. First, find the flash drive. Then download the bios from the site. Rename the downloaded file to EVGAE699.bin and put it on a flash drive. And then everything according to the instructions.

Thank you @yurasicpark74, I have followed your suggestion, but I can only find an 8GB usb. Anyway, it works. 

I don't know if this is some kind of quirk or bug in the EVGA 690 boards, but I have flashed 3 different BIOS's recently on my ASUS Z690 board using a 32GB USB 3.1 drive with no issue's.