[chandu95]

I updated extras+info app today and now it shows denim in it. Even the firmware version matches denim version on MS website. Is this really denim??? How come l didnt use phone update... Pls clarify

[xandros9]

Probably just renamed Lumia Cyan.

Why?
1. It saves manpower and resources better used for newer endeavors.
2. Windows Phone 8.1 Update is a minor update and doesn't really change the underworkings of the OS.
2.5. Because of that, Lumia Cyan works fine.
3. No new firmware features are slated for old models like the 520's.

[chandu95]

If so Cortana alpha should be working for me. But it's not

[xandros9]

If so Cortana alpha should be working for me. But it's not

Firmwares and Windows Phone are separate entities, they're just served together.

Are you using Windows Phone 8.1 Update? (can you make folders? Does about say Windows Phone 8.1 Update?)
Also check your region and whatnot.
The current firmware designation does not affect Cortana's availability, despite many using Denim and 8.1 Update interchangeably.