The response by "Taskmasters" gives you good answers:
1. Britain
2. Constantinople
3. Anatolia
4. Constantinople
5. mountainous terrain
6. prefecture of Africa
I'll add just a bit of detail on the last couple of questions:
As to #6: Justinian, who ruled from 527 to 565 AD, worked to reconquer territories in North Africa that had been part of the Roman Empire, attacking the Vandals who had taken over North African territory. The military expedition began in 533. The prefecture of North Africa was established in 534, though it would take several years before managing to control insurgency and maintain peace in the region.
As to #5 and the extent of the Byzantine territory: The Byzantine Empire reached the height of its power. under Basil II, the Byzantine emperor from 976 to 1025. He extended Byzantine rule into the Balkans, conquering Bulgaria. He also extended Byzantine power into Mesopotamia, Georgia and Armenia. But the Byzantines never extended their power north of Italy, as the Alps mountain range is a substantial geographic barrier.
