I've noticed that since I became a ranch hand, posts made as a greenhorn aren't reflected that way - they show me as a ranch hand - if that makes sense.
Yes, old posts get updated. The status always shows your current status and not the status when the post was made. The exception is that UBB caches pages so sometimes you may need to make a change to a page before the status change is shown.
Yes and No...with greenhorn you can going out with young ladies without being negatively accused either you have big bucks and drive fat hummer or a paedophil ... just joking anyway ...