5
If your existing answer had received votes (up- or down-), I would restrict edits to improvements on that answer. If it had not yet received any votes, I say go ahead and change it completely if you want to. I believe that edits within the first few minutes of posting are absorbed into the "initial" version of the posting. After that, there's an edit history....
2
Yes, Answers that don't answer the question should be flagged as "not an answer" (or spam/rude/etc as appropriate). They'll then go to a queue for further review. Users with higher-level moderation privileges can then cast votes for deletion.
It's easier when the answer starts with "Not an answer per say [sic]"
Sometimes such not-an-...
Only top voted, non community-wiki answers of a minimum length are eligible
