List of Federated Instances

Hi everyone, I have some technical questions regarding federation. Answers backed by documentation would be perfect.

1. Is there a way to get the list of federated instances of a specific instance?
2. (Regarding question 1, should this consider active followers between instances? If not actively defederated/blocked, when one account follows another from another instance, the two instances get federated, right?)
3. Can I get a list of actively blocked/defederated/muted instances?
4. How does this change between applications? Are for example Lemmy and Mastodon the same?

My goal is to possibly create a graph/network analysis.

Thank you for your help.