CLEAN FLASH WITH AOSP RECOVERY

1.) Download the boot , dtbo and vendor_boot images l 2.) Connect To Pc

3.) Reboot to fastboot ( press both power_button_key + vol_down_key ) and follow the steps as given below.

fastboot flash vendor_boot  vendor_boot.img

fastboot flash dtbo dtbo.img 

fastboot flash boot boot.img

fastboot reboot recovery

Select Wipe Data/factory Reset & Confirm

Select 'apply Update' From Adb

adb sideload  Rom_Name.zip

Select Wipe Data/factory Reset & Confirm

After Installation Complete, Reboot System.

( optional ). Reboot to recovery to sideload any add-ons ( e.g magisk, firmware, gapps etc )

DIRTY FLASH ( Without data format )

1. Reboot to recover by holding power button and volume up simultaneously

2. In the recovery menu select Apply update through ADB

3. adb sideload Rom_name*.zip ( or drag down the rom zip to cmd )

4. After installation complete, Reboot system.

Change partition slots ( optional )

If your device does not change slot automatically, you can do it manually just follow the given steps. adb reboot bootloader

fastboot getvar current-slot

fastboot --set-active=b ( for eg. your current active slot is A so you would want your current slot to set be on B )

fastboot reboot

Linux fastboot permission issue

Try using sudo $(which fastboot) instead of fastboot

for eg.

sudo $(which fastboot) devices

sudo $(which fastboot) flash vendor_boot  vendor_boot.img

and so on.

How to flash rom with TWRP?

• Before doing the following you should be sure that your bootloader is unlocked.

• Download twrp-TheStrechh-RX.img from HERE, and platform tools from HERE Windows and Linux

• Extract platform tools in C:\ and copy boot.img in folder.

• Open terminal (CMD) in local folder and paste this command fastboot boot twrp-TheStrechh-R2.img , then click enter.

• Device boot in TWRP interface go to Advance and select Flash current TWRP and confirm. Done, you have TWRP installed fine, now can reboot system.

First option

Download ROM, then go to Install -> select your ROM.zip -> Confirm.
Back to TWRP Home, Go to wipe -> format data -> wipe cache from advanced wipe (For clean flashes only. If you are just updating, ignore this step).
Back to TWRP Home, Go to reboot -> and change active slot. If active slot was A, select B. Or if active slot was B, select A. There is an indicator there shows active slot.
Back to TWRP Home, go to Advanced -> flash current TWRP . If you forget this step, you'll lose TWRP after reboot.
Now reboot system and enjoy.

Second option

Boot in TWRP -> format data -> yes
Install the ROM with adb sideload -> adb sideload rom.zip in adb termianl.
Back to TWRP Home, go to Advanced -> flash current TWRP . If you forget this step, you'll lose TWRP after reboot.
Reboot recovery and flash the gapps of your choice.
Now reboot system and enjoy.

thanks priyanshu for this guide writing.