Event+ Registration Bug & Custom Field not working

Created some event listing to test run.

During testing, as a vistor I clicked on the I'Attending button which brings me to backend wp login screen then i click on 'Register' and it gave me a blank section(shown on attach screenshot). Please advice.

And also some question-
1. What does Additional Field does in the Event+ Setting page?
2. If I would like more custom fields on the register form for data collection does 'Additional Field' function helps? If not, any advise?
3. Where can I view those 'data' collected?

Hope to get replies soon as I am trying to develop the client site on tight deadline.