Mobile Flash solution
MTK CPU:
1. Firstly setup the MTK USB driver your pc.( Download MTK Driver)
2. Connect the mobile to pc using USB data cable. Mobile must be switched off and disconnect the battery from mobile.
(Tecno in3-h3721d Firmwaer vartion= IN3-H3721D-N-181017V55 Download Link ).
3. No need to press the boot key to connect for flash.
4. Browse the flash file from your pc.