[LG V20 Questions & Answers] Team DevDigitel:
fasboot flash recovery "put the name over your recovery here" .img

so it should be

fastboot flash recovery twrp-3.0.2-1-h918.img

pull battery

then try to get into recovery with the power and volm down key method

if not.. lets clean up and start fresh okay?

put your phone into fastboot and run each of these 1 by 1 and press enter as you go..

fastboot erase recovery

fastboot erase system

fastboot erase cache

fastboot erase userdata

fastboot erase misc

fastboot erase fota

fastboot erase boot

then go ahead and pull battery, go back into fastboot and do the following. You should already have this done but i need us on the same page..

you need to pull the boot.img from the STOCK rom for your device. Get it out of the downloaded rom zip and put it where fastboot is

as well get the twrp.img for your device and put it there also. Example for me C:/ fastboot and c:/boot.img c:/recovery.img all in the same spot, then back to your cmd window.

*Make sure the "boot.img" and "recovery.img are named to that, or youll need to type the name as you have the files saved*

cd c:/fastboot

fastboot flash boot boot.img

fastboot flash recovery recovery.img

then un-plug and pull the battery when done and try to get into twrp with the manual key combo.

if so, you need to still go ahead and use twrp to wipe everything, depending on the "resize" and stuff you said you did you may need to do the advanced opions of twrp and use it to format-repair data- and format every partition using EXT4. This should put the file system back to how it was supposed to be.

once done and formatted, system should mount and be ready for the flash of the full stock rom.zip you 1st were using.

Flash it using twrp and wait and let i boot up..

as well reading your commands your typing adb stuff for fastboot mode? that wont work.. adb is only when device is booted or atleast booted state like on lg splash screen if your boot.img has been modded to do so. So no Adb here... just put your files with the fastboot directory and do the above commands with the phone in the bootloader state of fastboot. Where it has the text down left side of screen. " hold vol down and plug phone into pc from a off state puts it into fastboot"

My directory is C:/fastboot

yours is C:\Users\twidl\Desktop\platform-tools\

so in platform-tools you need to have put a copy of twrp and the stock boot.img....

your twrp file " twrp-3.0.2-1-h918.img " should be in that folder as well as you need to pull the boot.img from the stock rom, dont use lineage as its not stock.. as well as you need to have a copy of that stock rom sitting on a SD card that works so once we get into twrp you can put that sd card in and flash from the sd card. Im not sure why you were directing fastboot to a diffrent directory to get twrp installed, it wont install files from remote locaions, just keep it simple and place the files you are needing to use in the same spot fastboot is.

furthermore, dont use fastboot and try to push the rom to the phone as this isnt the correct way to install it. You need to use fastboot to wipe and get the phone ready for twrp and allow twrp to do the install. just take it slow and read above info and let me know if you have questions BEFORE you start shooting anymore commands.