I installed Opera mini from the Microsoft store. My phone is a lumia 640 running Phone 8.1.
This version of Opera mini on this phone is incomplete at best. Nothing like the installation on my Android phone.
Where is the Opera button on the lower right side which has a simple button within to shut down the app as you would a program on a laptop? Forget about all the other options within that menu area.
I was going to describe the differences but what's the point? You already know it is not the same and it's annoying.
I only installed it to save the data downloaded so that supposedly is working according to the app's report.