If there are 2 rubbles (1 x 1) diagonally, can a hero (or a monster) have line of sight in diagonal, cross them diagonally or fire diagonally?

Sorry to my bad engish and thanks for your help

Yes, you can trace Line of Sight, move and shoot diagonally between two obstacles (or two figures, friendly or enemy.) An obstacle (figure) and a corner of the dungeon works the same way, btw.

FYI: It's better to ask such questions in the main forum. This sub-forum is intended for home brewed content (ie: stuff fans made up by themselves), which is probably why your question has gone unanswered for this long.