If I apply ED to Cornell, am I not allowed to apply early action elsewhere? Since even though I love Cornell, theirs a big chance with all Ivy's that there is a rejection, and I want to try other options.
You can apply wherever you want if you ED to Cornell. But you can't apply through any sort of restrictive admissions processl. If you are accepted ED, you are expected to immediately withdraw your other applications and submit your deposit. Usually ED implies restrictive admissions and EA does not, but you'll want to read the details of each school's policy. Because if you get in to 2 or more schools where they expect you to withdraw your other applications, you'll probably end up not getting into either.