As in prior years, students can only present more than one presentation if the topics are truly different. If your presentations are variations on the same theme, only one will be allowed. You can make the changes you mentioned when you submit your Abstract. If your topics are truly different, please contact Jennifer Rockhill, by email, firstname.lastname@example.org.
It’s understandable that summer researchers would like the Abstract deadline extended. This Symposium is an opportunity for undergraduate students to present research conducted at any time during the past year.