The phone comes pre-loaded with Windows Phone 8 firmware, but you will be able to upgrade it to 8.1 + Lumia Cyan update in the coming weeks. (windowsphonearea.com)
The new Lumia handset runs Windows Phone 8.1 with Lumia Cyan update and supports firmware over-the-air (FOTA) updates. (gadgets.ndtv.com)
Starting November 7, the Lumia 635 with a fast, quad - core chipset and preloaded Lumia Storyteller app, will be available at Cricket Wireless stores and online in Cyan for $ 99.99 with activation. (windowscentral.com)