Question about the helicopter (Resident Evil 7)

Why the helicopter,which Chris Redfield took Ethan belongs Umbrelle? As I know,the action of the seventh part of the game takes place after the sixth part(and there are Redfield was part of the BSAA and he fought AGAINST UMBRELLы),and here's why he Umbrellу? Where did Lucas after passing through the test area? as I understand it,when Ethan went down to the underground laboratory,on the radio he heard that Lucas was working for special forces or any military organization and they gave him the serum against Evelina.After the ending about him was nothing said.And why all the world's population turned into zombies? The action of the game takes place 15 years later the contamination and destruction of raccoon city,but as I know,the virus then-T has spread all over the world and all the people turned into zombies and in this game for some reason, all alive and well! Answer,but I DO not understand!