Intel I225-V/I225-LM Rev 1.x Lan Controllers Firmware Version 1.89

no, the dump works with the mac address of the mazi machine, I'm sure it doesn't come from the firmware but from the drivers, mini CAT6 cable or others 

Downgrading drivers is a classic and best way to fix issues with cheap Intel 225V cards.

Versions v1.4.38 v1.1.3.34 and the one that comes with Windows (it says MS Corp because comes by defaults but it's no a generic driver, It's actualliy from intel) and propably fixes any issue better than otrher.
I'ts worth a try.

If all hope is lost then try clearing CMOS, reinstall windows, whatever. i don't know if you can force a firmware downgrade with EEUPDATEW64e.exe. Firmware is not the issue because almost all here have the same device I225-V (3).

I updated the firmware to the latest version available here, to try to solve the problem with crashes when opening online games, but it did not solve. I would like to downgrade to some older version. And it seems that this tutorial does not work to downgrade to 1.4.5.

you can't go back with the firmware but as Alexander says very well, have you updated the drivers but not confused with the firmware 

this firmware worsened my connection in games, I formatted windows and it didn't solve it, can someone help me to go back to version 1.68? I don't have backup.