2) Building Churches in shape of Cross is pagan practice?
3) Christians developed it. They used some elements from Greco-Roman basiliacs, but it is essentialy different.
4) From when Ancient Slavs=Ancient Greeks+Ancient Romans
Were have I mentioned basilica? Where hava I mentioned it was a pagan temple for that matter? I did not. I know very well the origins of the basilica i.e. the Roman Tribunal. So allright, Christian church has origin in Roman tribunal, no argument there.
However, Orthodox (Byzant, eastern) and Catholic (Roman, western) architecture (churches included) show great difference, since Catholic architecture absorbed Roman architecture, while Orthodox absorbed Greek architecture.
The same happened in central Europe, Christianity assimilated central European slavic wooden style. Leave your religious zealotry aside and you will see clearly the patterns.
If I remember correctly Iconography wasn't always allowed in early Christendom (it was blasphemy) but they had to accept it to win over the heathens, who represented visually their Gods. Christianity at its core is nothing more than Jewry (hell, even in the bible it says we should accept them as "chosen people")