Can you go into more detail with (1)? It's unclear to me how vector clocks could help with, say, a fast-paced FPS. The "small adjustment" might often be bringing a dead character back to life, if his bullet packet's vector clock claims he shot first. (Hack potential, too...)
There is always hack potential. All the server can do is make sure that the claimed move is legal (eg fits the rules of chess) and realistic (check a string of inputs to see if they probably have been made by a human).
As for the adjustment... Yes bringing a character back to life after a momentary error, in one place on the map, as seen by one person, is a small adjustment that happens rarely.
