Facebook – What happens to pictures, videos and audio messages in recipients inbox when facebook account is deleted

No. Each message is transacted with a unique email ID. The inbox for each user is independent of messages. i.e., the message you send is not linked and stored internally with the inbox of the receiver.

Each mail transaction like draft, inbox and trash act independently with regards to the email user. Hence, manipulating any message will only reflect your email.

At least no major service provides allow such cross deletion.

Any messaging system doesn't allow you to delete item from another's inbox by deleting your own. Gmail will treat a message as a thread. So if you have a message in the inbox and also have stored it in a particular label, deletion of that message from the inbox leads to deletion from label.

However, it does not remove from your friend's Facebook inbox, it's that simple.

Ok.

What happens? Well, depending on the path you follow, different things.

For example, you can be asked to fill out a form that asks you questions regarding information relating to your account, as is described in this article. Then, as that article says, someone at Facebook reviews the information and checks it against what they already have.

Once you report the account as compromised, it is locked down. Meaning only the people at Facebook can access it. Then, you must provide enough information to prove it was yours. Then, you get access to the account to fix/change back any information that was changed (like the email address the password would get sent to, etc.)