You can still get Cortana, even if your carrier has block/not rolled it out, provided you can do the manual updates.

Worth noting that some carriers will intentionally block the update for a while with phones already out there based on your regional settings, this is so they can sell the new ones with it enabled as a selling point. Hence the 630 got it before you could update the 920… but as I mention you can still get it, provided you can upgrade your phone to 8.1 and relatively recent updates, newer the updates the newer the version you will get and the more “languages and accents will be supported”.

Also worth knowing – you might already have it if you are the latest update, it might be that it is just not switched on, default is “off”… On most older phones, including 920, it is still classed as a “Beta” application which replaces the existing speech support built into those devices since 8.0…

Finding it if you already have it: –

open “Settings”

• you will be on the default tab “system”, swipe to the side so you are on “applications”, if it is available with your current configuration, it will be listed. 
• Click “Cortana”.
• Turn it on.
• Restart the phone if required.
• Hold down search button to start it.

If blocked or not visible – getting it if you do not have it: –

This varies somewhat depending on your device and update availability… easiest thing to do is change everything to “English (United States)” turn on Cortana and then try adjusting things back to your region one by one… when Cortana stops working change whatever you last changed back to “English (United States)”

The three areas to change are “Region”, “Language” and “Speech”. Then you need to turn it on.

Cortana will only work if “Language” and “Speech” match and Cortana is available for that combination.

Here I have it working with both English UK and US note that “Language” matches “Speech”

open “Settings” 

1. Under the default tab “system” scroll down and go into “Region”.
2. Change “country/region” to “United States” (if Cortana not available to you).
3. Change “Regional format” to <your desired format> (for me “English (United Kingdom)”).  
   • This preserves your currency and date format.
     
4. Click on “Restart Phone”.
   
5. Check for any updates, and install them, restart as required.
   • This will get Cortana and other updates if not already installed.
      
6. Under the default tab “system” scroll down and go into “Language”.
7. Change the language to match the region setting (“English (United States)”).
8. Click on “Restart Phone”.
   
9. Next bit differs depending on whether Cortana is available in your local language version… including the variations in English accent and pronunciation.
   • If it is, available in your language/accent.
     1. from within “Settings”.
     2. if on “system” tab, swipe to the side so you are on “applications”
     3. if available you will see Cortana at or near the top.
        
   • If it is not visible within “applications” tab (within “Settings”)
     1. Go back to the “system” tab.
     2. Scroll down to to “speech”.
     3. Go into “speech” and change the “Speech language” to “English (United States)” … or another one that is currently supported by cortana…

        Note: Depending on your current phone setup, you may need to download, then go back into this and reselect it to get it to install, follow the prompts, reboot as required and then check for any phone updates, which will get the updated speech package which includes cortana.

     4. Make sure “speech” matches “language”.
     5. Once done with all the updates/install of language packs, as above, go into settings, swipe to side to get “applications” tab… and you will see Cortana listed… open it and switch it on.
     6. Restart phone if required, hold down search button an say hello to Cortana.