@babyangelhp can you send me the FULL boot log? you had already posted this error message but i want to see how far it gets without this.
as for restoring stock... don't worry it's actually really easy to do (even if your system is completely messed up)... you just reverse the steps you took when telling the router to boot openwrt... unfortunately i don't have my UART handy (and it's a little hard for me to take the router offline)... maybe @pjgowtham or @andreykiselev can double check (it's in the uboot menu.. you basically set the
0.. then remember to save the settings and reboot)
now that you're on stock, to install openwrt you're going to setup a tftp server (on a pc), connect it (via ethernet) to the router, setup the IP settings (they have to be on the same subnet) and boot from it (again from the uboot menu)... there are online guides for setting up a tftp server.
anyway, once you've tftp booted (you're going to use the "initramfs" file, not "sysupgrade" or "factory") then you'll just do a
sysupgrade and all should be well. oh and you'll need to make sure those
flag_try_sys_failed settings are setup so your system is set to boot from sys2 (that is, sys1 should be "failed")
however, it would be nice (since you have an UART anyhow) to first install openwrt the "regular" way, save the bootlog, and then do the tftp thing (you won't need to restore to stock first). there's probably a bug there and it would be nice to at least have it filed or known.