Microsoft's VP and Manager for the Windows Phone Program, Joe Belfiore, has tweeted that an update to the Facebook Beta app has been released to enable usage on devices with 256MB RAM.
The reworked Facebook app was launched in April for WP8 and has been available for WP7.x users since late August. However, WP7.x devices with less than 512MB of RAM had been left out from the initial release. Now, Microsoft has launched this app for WP7.x users who have phones with 256MB RAM such as the Lumia 510 and 610. Microsoft has been slow to roll out this app but now it seems they have all of the devices covered for wider testing. The app is still under development and has been receiving plenty of updates since its initial launch to bring it closer to the iOS and Android versions.
This update also brings in some bug fixes (Live Tile and notification bug, where the count does not clear even after viewing the notifications and/or repeat notifications) and performance boosts.
It should be noted that the app has different version numbers on both the platforms but makes use of same UI elements and provides same features. The updated application can be downloaded by visiting this link from the phone as it will not show up in the Windows Phone Store.
Source: Joe Belfiore on Twitter