Hi Heather,
It's a principle that students can change their answers at any time until they end the exam. Students so often accidentally press submit, or spot a typo just after submitting, that I don't think it's fair to limit the number of times they can submit.
So in order not to allow students to work out the correct answer by repeatedly submitting answers, for summative tests you should turn off feedback: as Martin says, turn off "show answer state" and "show current score".
I wouldn't have "allow reveal answers" turned on - if your students can corroborate, then one student could pass on the correct answer to another. Also turn off "try another question like this".
Is there a reason you want students to be immediately given feedback on individual questions, instead of waiting until the end of the exam.
Christian