Sorry this will not be any use to you now, (did you get the job btw) but maybe for someone else
1) wear something smart as you would to any other interview (unless you have been instructed otherwise)
2) Not sure, but they may give you a scenario or ask you to sell a “pen” to someone (iinterviewer)
3) I think this depends if its a group assessment
4) Sometimes, it depends on what they actually want to find out about you