Nullity relates to marriages that are not considered legal (despite a ceremony having taken place), whereas Divorce (dissolution) relates to marriages that are legal (but have broken down due to various circumstances).
Yes, provided that the bride (or groom) is not the one being surprised. Note: A wedding where the bride or groom is unaware of the event, could end in either Nullity, or the ceremony not taking place at all.
The entire phrase 'Never Validly Married', simply means never having been married, however the word 'Valid' refers to marriages that are legally binding. Marriages that a terminated by a 'Declaration of Nullity' are not considered to ever have been legal, therefore 'invalid'.