Will I get my passport back the same day if I cancel my ed visa?

Yes cancelling the 'extension' is cancelling the visa despite the nonsense semantics.

First of all, you cannot cancel an ED visa, you can only cancel and education extension.

Second, you'll receive your passport back immediately. They might not even take it from you other than to cancel the extension and hand it back, or they might make you wait and then call you up to collect your passport.