If you're already running Arrow Os and have ditched MIUI, you should be able to update without any problems, without having to check your firmware version.
Great, thanks! But if I'd like to know it how would that happen? And can I update the firmware without problems?
I don't really know how you would update your firmware... but do you really need that?
I think you can do that. I did that before and it is working but i suggest you to check anti-rollback version before flash to prevent brick. This is guide to check it.