Lumia 630 is one of the worst product of Nokia. Because is has only 512 mb ram so it is hanged many time. The main thing is that it has no flash no front camera which is need for everyone in todays life.
The navigation key is on the display thats why the navigation key covers the small part of display. Since it has no flash so you can not take a sharp photo in low light condition. Since it has only 512 mb ram so you can not play heavy game.
When I keep many application it become slow only because of 512 mb ram. At last I want to say it is not good product and I am not recommended you to buy this this product.