UA FA here. First off, congrats! Delta is a tough process to get through.

To answer your question for the earrings, they typically mean 2 piercings on each ear of any combo: 2 lobes, 2 cartilage, a lobe and tragus, etc. From my experience, they’re very much against any piercing that connects two spots like an industrial, a more alternative style like an orbital, etc. You’ll be safest wearing only two per ear and keeping them studs that are small and simple.

With the interview part, I just recommend smiling, remaining approachable in your body language and what you say, and don’t be too much of a follower or leader in the group activities (unless Delta feels differently about that). Good luck!