[Prince2]

I want to flash a system IMG custom rom for my SPD sc7731e Android 10 go edition when I flash system IMG or erase system IMG it tells me error unknown reason .for recovery IMG it hangs on writing recovery also same for vbmeta when flashing blank vbmeta IMG is there any solution for this?

[hovatek]

I want to flash a system IMG custom rom for my SPD sc7731e Android 10 go edition when I flash system IMG or erase system IMG it tells me error unknown reason .for recovery IMG it hangs on writing recovery also same for vbmeta when flashing blank vbmeta IMG is there any solution for this?

Unisoc is done differently.
Confirm that you've unlocked bootloader

[Prince2]

Yes unlocked bootloader via SPD identifier token method!

[hovatek]

Yes unlocked bootloader via SPD identifier token method!

For the vbmeta, custom recovery and root thing, see https://www.hovatek.com/forum/thread-32678.html
For the system image, try

Code:

fastboot flash -S 100M system system.img

[Prince2]

For the system image, try
Code:
fastboot flash -S 100M system system.img
Tried Works
But say data file to large
Or Unknown Reason.

[hovatek]

For the system image, try
Code:
fastboot flash -S 100M system system.img
Tried Works
But say data file to large
Or Unknown Reason.

share a screenshot

[Prince2]

did as instruction but this occures

[X3non]

did as instruction but this occures

you should post info_image output from your stock vbmeta and also post the command you used to create this new vbmeta