Keep in mind that Ban Appeals are on a case-by-case basis, so some answers might not be sure-fire, as well that I am only 1 staff member on the team and opinions may vary amongst us.
1) The Appeal would Ideally include:
-The reason for the ban
-Why (in the banned person's opinion) they should be unbanned
2) Because our staff has a diverse range of timezones, and only Admins can see the actual ban appeals, I can't give you an answer on when they're checked, but I can't imagine less than once a week.
3) Again, these are often case-by-case bases. An unbannable offense could be something like perhaps disturbing peace with some players (such as destorying their builds without permission) and mistreatment of staff (if both parties talk it out/it was a misunderstanding).
It is always important to reach out so we can handle cases in a very calm and professional manner. Please note that some offenses can be more forgiving than others based on things like history of offenses, warnings given, and past issues with the server. Thank you for asking!