You have to be 100% honest. If you don't, you will lose the opportunity to get PR.
According to your questions, I would say:
1. Yes, you have to write down your UCI number in all forms and documents.
2. You have to write YES. You got a certified copy and that it is a proof. You have to write down expiration and issuing date as well as the passport number.
3. If previous refer to other attempts before the current refugee claimant you have, it depends on if did or didnt. Just read clearly. If refers to the current claimant, you have to say: YES because you are in a current claimant.
Sources: I had the same situation like you and I already got PR.