Each visa has a set of regulations. You must have an English test before lodging an application for a 485. Your AAt will confirm the refusal. They must confirm the law. It has nothing to do with letters from your university or subsequently doing an English test.
You can't reapply now as it is more than 6 months since completion.
I assume you are on a bridging visa now. If that is the case you are Section 48 barred from applying for a 190.
Please tell your friends. Go and see a registered migration agent before you start, unless you are absolutely sure.