[Steve44]

A zero-zero seat means it can safely be used at zero speed and zero altitude. It needs to give enough height and separation to allow the parachute to open, not just get the pilot out of the aircraft.

As far as I'm aware all modern seats can do that. Earlier ones for example could eject at low altitude it there was enough air speed to open the chute and slow the pilot down before landing.

Regarding the other part of your question, I believe some seats can change direction dramatically in flight. For example if the aircraft is in a steep bank the seat can steer to give more height, but I don't know much about those.

https://martin-baker.com/about/ has some information about seats and their history.

edit : In https://www.youtube.com/watch?v=LbMg2pQW924 you can just about see the seat begin to change angle from horizontal to vertical. It's very fast but does seem to be there.