No need for any backup
First download all required files:
- IMEI Repair Tool Download From Here
- Root Kernel Firmware Download From Here
- COMBINATION_G532FXXU1AQK1 Firmware Download From Here
- Repair Firmware From Here
STEP BY STEP :
1- Flash firmware for root.
2- Flash root kernel.
3- Boot to recovery mode and wipe data and cache.
4- Run the imei repair tool wait for phone to boot into download mode.
5- Flash combinatuin firmware, The device will boot and show android logo with error just skip it and boot the device to download mode.
6- Flash full firmware.
7- Done, Original IMEI has been restored.