Why can't I change my Facebook url?
well, you can only change it ONCE (not twice)
Why suddenly on facebook , i can see 'facebook user' and i cant answer to this person anymore ?
If it says you can no longer message them, then yes.
How to hide my facebook birthday so people cant see it on the calender at the top right of facebook?
change your birthday too another date then near that date change it again
Why cant I log onto facebook?
It's working for me.. Must be something on your end... Try restarting your device.
I cant see video in facebook?
Restart your computer and try again.