No, if you want to change your username then you must delete your account and create a new one under the new name.
The grey text is an action and is referred to as "slash me". The reason it's called that is because the syntax is /me <action>
Currently, only YouTube videos are supported. Include the link to the video in your status update and it will be displayed as an embedded video.
If you are having issues with another user in chat, feel free to use the mute button conveniently located next to the users name on the user list. Muting removes the user from the chat window allowing you to control who you see and don't see in chat.
The only users that can send you messages and leave you comments are your friends. If you are having issues with a user, simply unfriend them and they will be unable to continue.
If they are faking you, you must post a proof pic to your profile to first prove the validity of your claim. Proof pictures must include your username, the name of this site, the date and the username of the user you're calling out on a handwritten paper sign. Once this has been done, click "Help" and report the issue.
Click "Edit Your Profile" and at the bottom there is a button to delete your profile.
Member type is just a textual indicator of how long you've been on the site. It also serves a greater purpose of indicating which profiles belong to the site's staff. Don't be fooled by imitators, if it doesn't say "Official Staff" then the person is in no way affiliated with this site.
Simply put, you cannot. Some users put "officially verified" on their profile, that's just part of their "About Me" and is absolutely meaningless.
Nudity, defined as nipples, genitalia, and pubic region (including pubic hair), is not allowed and should be reported immediately. Underwear or subjectively, "too much skin" is not considered pornography.