Ranking

Those are awarded manually by the CiC or SiC of an alliance. How those are assigned is up to the alliance policy.

Veterans, by default, get to see shared forums.

Officers, by default, get to see shared forums and get to adjust the rank of lower players (eg from Trial to member or veteran). They also, by default, get to invite players to the alliance and to change diplomacy. The SiC or CiC can change the default values and some do by removing the ability to invite or to change diplomacy.

I'm a CiC in 4 servers. I use veteran status kind of as a rank reward, meaning depending on the world if you progress to a certain level I award veteran status.

Officer status I give to anyone that 'gets it.' What I mean by that is anyone helping other players, any one helping with POI in any consistent way, anyone who seems to get the big picture beyond the development of their own agenda I make an officer.

Sometimes you have a bunch of those, sometimes not so many.