We'll take the third one. Leadership is not magic that comes out of a leader's head. The leader learns how to get the job done and still keep the group together. Leadership differs with the leader , the group , and the situation . No leader can take over another leader's job and do it the same way.
Groups are different, too.
A great football coach might have difficulty leading an orchestra. A good sergeant might be a poor Scoutmaster. So when a leader changes groups, he changes the way he leads. Situations differ, too. The same leader with the same group must change with conditions.