take the originals to the office - they will site them, record the relevant details (document numbers) on the system, and you keep them. they don't retain copies of any POI, just record the document numbers

ftb is different to any other payment - for ftb, they take your details at face value. for anything else, they need to see 100 points of ID. it actually comes up to more than 100 points you need though, cos anything you use to confirm proof of birth (or arrival) in australia (birth certificate or passport) can't be used for your 100 points