Sure....here's what I did when I sort-of bricked the WNDR4700. I first flashed it back to the Netgear firmware and made sure that worked before going to OpenWRT 21.02. You might be able to flash it directly to OpenWRT, but I didn't try that so don't know.
-
Download the Netgear firmware: https://www.netgear.com/support/download/?model=CENTRIA+(WNDR4700%2F4720)
-
Plug the router in and then hold down the reset button for a really long time. (It will power off an on maybe a few times, but just keep holding that reset button down.) Eventually you'll get a green flashing power light on the router.
-
Connect your computer (via a network cable) to one of the LAN ports on the router. Manually set your computer to an IP of 192.168.1.10, subnet mask 255.255.255.0, router 192.168.1.1.
-
Open up your terminal (again, I'm on a mac. Would work same on Linux, I presume. Don't know what Windows folks use for a terminal). Then run:
cd <whatever directory you saved the firmware file in>
tftp 192.168.1.1
binary
put <insert firmware filename here>
Then wait. It may take 3 or 4 minutes to transfer the entire file. So don't be impatient. Once the transfer is done, I believe the router will restart on its own and should (hopefully) be running again.
Hope it helps!