Did you sign up with Google and/or Facebook only?
The same way. Swipe left to delete.
Planned to improve and fix in 5.1.
If fake Vine is still used and is helpful I will fix the UI (currently broken locally) - which is the reason why I have disabled it at the moment.
Enable Fallback composer from Global Preferences.
Take a screenshot on your device.
Currently not possible, but I plan to add in multiple usernames per user soon.
Customer support service by UserEcho