This process only work on MTK Chipset.
1- Install MTK Driver.
2- Download SP Flash tool.
3- Download MTK Firmware.
4- Run SP Flash tool.
5- Click on Scatter-Loading and assign the path of stock rom.
6- Select Firmware Upgrade as shown in image
7- Click on download.
8- As soon as Flashing is completed, Restart the phone.
9- Gmail Lock has been reset.