Professional (paid) service tools. These are the most reliable for bypassing bootloader security.
Yes. If you download the Android 13 stock ROM for your specific model number, the flash tool will overwrite the old OS with the new one. This is often faster than waiting for an OTA rollout. nokia g21 flash tool full
If you only wanted to update or unbrick without full tool details, let me know and I can provide a simpler summary. Professional (paid) service tools
Use a high-quality USB cable and install the necessary Nokia USB Drivers or SPD/Unisoc drivers. Essential Tools and Files nokia g21 flash tool full