Chosen Solution

You can replace the broken glass of lumia 900? The official information I received is that I can only replace the entire screen.

Marco Matosm that is correct. Just like the iPhone, the digitizer and the LCD are fused together and should be replaced together

if it isnt possible to replace just the glass on the lumia and iphone then why are there so many places that sell JUST the glass?

It IS possible but requires specialist machinery to separate the LCD from the broken glass and then you can stick the new glass to the existing LCD. This is only feasible for repair businesses though , as the machines cost a lot more than the phone does brand new!