So many users have been wondering how they can Upgrade there Lumia windows phone to windows8.1
Windows 8.1 is very lovely and fixes most issues with the Windows 8 on your Windows Phone
In other to do this, you would have to sign up for developer preview in other to download it
Checkout the Pictures of the Windows 8.1

Notifications + Actions Settings
[img]http://diptimayapatra.files./2014/04/041414_1535_windowsphon10.png?w=620[/img]
The following screen shows the four actions buttons available in action menu. Touch on each of them to change from a list of settings. Checkbox showing “Show notifications in action centre when my phone is locked” will make the action men available while screen is locked. Further, the apps that are enabled notification are displayed below.
[img]http://diptimayapatra.files./2014/04/041414_1535_windowsphon11.png?w=620[/img]
New settings or Changed Name
[img]http://diptimayapatra.files./2014/04/041414_1535_windowsphon12.png?w=620[/img]
Storage Sense, Project My Screen and Sync My Settings
[img]http://diptimayapatra.files./2014/04/041414_1535_windowsphon13.png?w=620[/img]
The Project my screen page has dependency on USB connection, however I am not able to do it at the moment, I would update about this on another blog post.
[img]http://diptimayapatra.files./2014/04/041414_1535_windowsphon14.png?w=620[/img]
Sync my settings has following settings.
[img]http://diptimayapatra.files./2014/04/041414_1535_windowsphon15.png?w=620[/img]
Advertising Id This is a new setting; unfortunately I have no data on these settings.
[img]http://diptimayapatra.files./2014/04/041414_1535_windowsphon16.png?w=620[/img]
The following screen is for the Advertising Id settings, the settings are somehow related to the advertisement. I would update about this in another post.
[img]http://diptimayapatra.files./2014/04/041414_1535_windowsphon17.png?w=620[/img]
All new Store app
[img]http://diptimayapatra.files./2014/04/041414_1535_windowsphon18.png?w=620[/img]
[img]http://diptimayapatra.files./2014/04/041414_1535_windowsphon19.png?w=620[/img]
[img]http://diptimayapatra.files./2014/04/041414_1535_windowsphon20.png?w=620[/img]
[img]http://diptimayapatra.files./2014/04/041414_1535_windowsphon21.png?w=620[/img]
New Speed Dial
[img]http://diptimayapatra.files./2014/04/041414_1535_windowsphon22.png?w=620[/img]
Revamped Calling History
[img]http://diptimayapatra.files./2014/04/041414_1535_windowsphon23.png?w=620[/img]
All New Calling Screen
[img]http://diptimayapatra.files./2014/04/041414_1535_windowsphon24.png?w=620[/img]
All New Ringer Settings
[img]http://diptimayapatra.files./2014/04/041414_1535_windowsphon25.png?w=620[/img]
WiFi Sense
[img]http://diptimayapatra.files./2014/04/041414_1535_windowsphon26.png?w=620[/img]
Calendar now accesses your location
[img]http://diptimayapatra.files./2014/04/041414_1535_windowsphon27.png?w=620[/img]
All New Calendar Look
[img]http://diptimayapatra.files./2014/04/041414_1535_windowsphon28.png?w=620[/img]
Finally the Background of Start Screen
[img]http://diptimayapatra.files./2014/04/041414_1535_windowsphon29.png?w=620[/img]

For full tutorial on how to do this Upgrade==> Read This

After the upgrade, you would be able to enable cortana

Microsoft releases new updates to 8.1 developer preview, includes bug fixes

Can lumia 520 also benefit from this? I stay in a place where there is 2g and 3g but the 2g is more stable. Will I be able to choose a specific packet data type (either only 2g or either only 3g) instead of the phone switching to the more stable one in the area.

irukandji89: Can lumia 520 also benefit from this? I stay in a place where there is 2g and 3g but the 2g is more stable. Will I be able to choose a specific packet data type (either only 2g or either only 3g) instead of the phone switching to the more stable one in the area.

You can also benefit from this upgrade, but you cannot switch to 3g only, likewise other big smartphones Like the Iphone
you can only select 2g and 3g