Hello fellow lemmings!

I’m a new lemming like many of you and I want to know a bit more about the inner workings of lemmy. So I just have a few questions

• If I’m part of instance A and there is a community C in instance B and I want to put a comment with a picture attached.
  • In which instance is the data (comment+picture) stored?
• Is it possible to migrate from instance A to instance B seamlessly while taking all my data?
  • If yes, will my username change from user@A to user@B?
  • If the username changes, how do my previous followers keep track?
• When I’m just viewing (not commenting) community C@B from instance A, is some amount of data (images/post text) is transferred from B to A?
  • If yes, is it kept for sometime or permanently?
• If I’ve subscribed to 100s of communities in different instances, how much will it impact my instance?

These are just some questions that came to my mind. I’ll post more in the comments as they come.