Is there a net covering the back

If you are talking about protective nets..the are behind home plate and down the 1st and 3rd base line

Along the baseline and behind home plate up to a certain height. Balls do go over it

Nets are not covering all areas

The nets are not everywhere just as Ralph mentioned

Yes

Yes every were that is need to be protected

I don't understand but it's a net covering along 1st base and 3rd base