I am running the developer version of gdr3 on my Lumia 520 and I cannot download the Nokia Camera app. When I search for it in the store it doesn't show but when I search for it from the link, it says "not available because the software needs to be updated or it belongs to a different country or region". Why is it so?
It's not for your phone at this point.
But you can get it use the Wi-Fi Proxy method way of hiding your phone's ID
Download SysApps Pusher and find Nokia Pro Cam and when you click on it, it is NOKIA CAMERA and use this method below.
One thing you might have to try this many times until it says
INSTALL then when you hit INSTALL it will stall and says "Attention required. Tap here" but don't tap just go back to your Wi-Fi setting and turn off Proxy but be sure to tap the check mark before you close it out or it won't go back to your actual Wi-Fi, then go back and then tap the "Attention required" and it should finish downloading and install. BTW you have to have AMBER installed too.