Questions about connecting with Dreampi

Hey! This is my very first post! I know you guys get these questions a lot but I couldn’t really find exactly the answers I needed. I want to play pso online, I played it as a kid and absolutely loved it. Before I buy the game I had a few questions though.
1. Do I need a unique serial number/key to play online?
2. Can I use a generic serial to play online? I’m not too worried about the cloud saves or my character, I really just want the experience.
3. Is the serial number tied to the disc itself? Like if I bought a used copy off ebay, but they post a picture of the serial number, is it possible someone else could use it or it is tied to that specific disc?

You can use a shared key, but you won't be able to participate in server events. A US shared key works with any US disc.

Okay thank you, I will definitely find a copy with the serial number so I can join server events!