You might be looking for official stock rom for Infinix Note 3 right because you messed up your device in the course of rooting and all those crazy stuff.
This Infinix Note 3 stock rom is Android 6 build. You can still update to Android N after flashing this rom.
To download this, you don’t need Opera mini browser for Android. What you will need is PC and a Chrome or Firefox browser.
I am a teacher and i have fun showing people how to do it themselves