Is it okay to list additional extracurricular activities in my additional information section on the common app?

Hi! I think you should only add more activities to the additional section if those activities are a crucial part of your application. You don't want to give admissions counselors more to read if it's not necessary. If you feel it is necessary go ahead and add it, if not I would recommend not adding.

I actually suggest not doing this unless your additional activities somehow connect to the ones you have already listed in the Activities section. The 10 activities that you input on this section should be your most important ones. Admission counselors actually look down on some students who add additional activities just for the sake of adding them. I believe that depth is more important than breadth in this section. So if you truly want to add something in the additional section, it's better if you elaborate further on the activities you have already listed rather than adding some extra ones.

Of course. You should do that if you feel that without mentioning them admissions officers would not have a complete understanding of who you are and what you bring to the table as a highly qualified candidate.

Good luck