In unix, it is conventional to put a "#" in front of commands when sharing information in forums. This serves two purposes.
1. Usually the prompt for the root user is "#". So this serves as an indicator that "this is a command that you type at the prompt".
2. A leading "#" character also serves as comment in shell scripts. Everything that follows becomes a "comment", and is not executed. This is a small safety net so that if someone cuts and pastes, they don't accidentally execute something they didn't expect or weren't yet ready to execute. For example if part of the command is a placeholder meant to be replaced by something unique to the target, you don't want to cut and paste and run the placeholder string.
As for how to delete old versions, please see this post: How to delete old versions