CDMA users can't use iPhone before iPhone4? is that correct? look at this page http://support.apple.com/kb/HT3939

Before iPhone 4, we have 3GS, 3G &amp; 2G but seem they (3GS, 3G &amp; 2G) don't have any model for CDMA network!! is that correct?

So CDMA users (who use Verizon, Sprint, Nextel, Cricket and Alltel carriers) can't use iPhone til iPhone4 which has a model support CDMA? Is that correct?

I am doing a research about iPhone, so i need to know the history of its.
Yes, it is correct.

Before iPhone 4 the only supported network was GSM, iPhone 4 model A1349 is the first iPhone to support CDMA network.