Easy-to-follow guides for each platform. Every one hides its delete button somewhere different, and many keep what you posted after the account is gone.
Not on every platform. Reddit, for example, keeps your posts and comments, and Discord keeps your messages, after the account is gone, with your name taken off. Delete the content first if you want it gone.
Deactivating or disabling usually hides the account and lets you come back by logging in. Deleting is meant to be permanent, though many platforms hold the account for a few weeks before they finish, and logging back in during that time cancels it.
Generally not. Download your data before you delete, and wait for the download to arrive, since some platforms, Discord among them, cancel a pending export when the account is deleted.
Platforms make account deletion one button and content deletion a thousand clicks. Redact bulk deletes posts, comments and messages across 35+ platforms from your own computer, so you can clear what you can still reach before the account goes. Check the results afterwards, since messages, content the tools can't reach and copies on other sites may remain.
Redact bulk deletes your old posts, comments and messages first, while you can still log in.
