1. Two vastly different films in the same genre could be Oblivion and Wall-E, or Alien and Juno, A film that defuse its genre could be Frozen because the love story is between two sisters, not a prince, and their taking control of their own fates which is highly unusual for a Disney princess film
2. Action conventions have quite a few, being action-adventure, action-duel, action-epic, or action-clock. Audience love have variety, but also know what they like. Providing many different types of conventions allows cinema to draw in more costumers
3. I mean simply they could have different plots and endings, as well as overall emotion (not sure what this question is asking)