Questions Related to Prussia of the Past

When is the earliest time we may reasonably call Prussia, Prussia?

What was the nature of Prussian dealings with Geats? Where Geats a kind of Goth?

Which is correct? Northeastern Poland was part of Prussia. or Part of Prussia was northeast Poland.

Is it true that Jablon-Dobki was a small village during WWII in which Germans killed as large percentage of the population for hiding Jews? Is it true that parties interested in modern international law have said that the killing in the area at that time was of such a nature and extensive enough to be called genocide?

Is it true that Prussians sailed to the island of Birka to trade with Vikings before there was a Sweden?Is the Town on Birka Sweden's oldest?
Is it true that an important route to the Byzantine Empire ran from Birka through Prussia?

What can I learn about Ducal Prussia?