I need help now with YT How do I change the barrier surrounding the video?
Usually it's black but mine is white! please help!

You might have dark mode on. You can check by going to settings and there should be a dark mode option. If that is on, turn it off and it should be back to normal.

its true for the one time

to change your username, you must:

1) make sure what the username you want to change to is allowed in this community

2) contact a administrator (for example, jaysl)

3) through pm, tell the admin what you want to change to

4) if the username is allowed, it will be changed in a matter of seconds (minutes at most)

~