Upvote:-6
I don't know for 787-8 or Ethiopian Airlines in particular, but I'm quite sure they won't allow you plugging in external USB drives, because of security reasons.
Upvote:7
Regarding the AC power port. Nowadays (especially if it's described as a generic power port) all of the major plug types are supported (US, UK, Europe to name just a few of them). An example can be seen here: Flyertalk link