What certifications do I need to import K-beauty to Australia?

First time importing cosmetics to Australia. I know NICNAS (now AICIS) registration is required, but the process seems complex. Questions: 1. Do Korean brands usually already have AICIS compliance? 2. Who handles the registration — buyer or seller? 3. Are there specific ingredients banned in AU that are common in Korean products? 4. How long does the approval process typically take? Any Aussie buyers who've been through this, your experience would be invaluable.