Could someone answer why in about on my 8x the os version shows as 8.0.10501.127 and have just updated my sons 520 and it shows 8.0.10517.150. Surely the os should be the same on both regardless to the additions that Nokia put on there? The reason i say this as i have noticed on my sons 520 at the top of the wifi icon there is a little arrow pointing away from the phone!!!
The OS version can differ on a lot of models. It can currently be one of four different versions, 8.0.10501.127, 8.0.10512.142, 8.0.10517.150, or 8.0.10521.155. Microsofts
update history page states that "Your update version number depends on your specific phone model and mobile operator." So I would say it's perfectly normal to see both phones on different versions. I'm on a different OS version to my Dad's Lumia for example. You probably won't notice any difference between either of them in terms of usable features though
The little icon on top of the WiFi symbol is just a data transfer indicator. This appears to be present on some peoples phones and not others. I'm not sure what the requirement is, as some people with the same model of phone have the indicators and some don't.