Xiaomi Router 3G questions

Installing and Using OpenWrt
22

This:
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I am afraid to continue until someone can told me that this is ok, also, if i install this, how can i back to stock if i do something wrong?
Also, will i get wifi automatically turned on or i must do something to turn on wifi?

Also, on this tut:

Summary

Actual installation via SSH:

  1. Copy openwrt-ramips-mt7621-mir3g-squashfs-kernel1.bin and openwrt-ramips-mt7621-mir3g-squashfs-rootfs0.bin optained from the OpenWrt download site to a USB drive or wget it directly via SSH to a location ( /tmp for example) on the router
  2. Switch to /extdisks/sda1/ (if copied to an USB drive) or to the folder on the router like /tmp if downloaded directly on the router
  3. Run mtd write openwrt-18.06.2-ramips-mt7621-mir3g-squashfs-kernel1.bin kernel1
  4. Run mtd write openwrt-18.06.2-ramips-mt7621-mir3g-squashfs-rootfs0.bin rootfs0
  5. Run nvram set flag_try_sys1_failed=1
  6. Run nvram commit
  7. Run reboot

I go there and find for files and download? http://downloads.openwrt.org/releases/18.06.5/targets/

Again, sorry for my non perfect english so i must ask more times to be sure.
Thanks