What type of questions will be asked during the interview round (and what’s the interview style?) and the writing portion?
Well my first suggestion is that you spell Elon correctly! 
Both my kids have attended Fellows week-end. Their interviews were fairly casual - there were questions related to the field of study for whatever program they were applying for, but otherwise it’s a friendly conversation. A lot of it depends on who conducts the interview. One of my kids had a professor whose subject area related to her fellows program, the other had a professor who was completely outside of the department. Both were very conversational and not stressful. The writing sample will come from a mini-class that you attend. No way of knowing ahead what that will be. The most important tip I can share is to make the most of the Friday evening reception; that event is as important as the interview and essay. It’s a great week-end, so just relax and have fun!