So 1º question:
When i create a branch and preview it as a learner, the student is offered the chance to skip to the next activity. I want to force the student to see at lest one of the branches.
Students aren't able to skip activities pass a branch. Meaning that they would have to do at least one branch in order to continue with the rest of the sequence.
The reason you can skip ahead in Preview, it's because you are a teacher and you might not want to go activity by activity until you hit the one you want to see how it plays. However, this behaviour is not allowed for students.
2º Question:
For example, i have an activity named (ISO, Aperture) and i test the student with multiple choices and he doesn't get the right answers, it is possible to switch automatically or reroute to the activity (ISO, Aperture)
I think what you are trying to do is to do a loop. But correct me if I'm wrong here... what you want to do is for the students to read some content about ISO and Aperture and then after this activity give them an Multiple choice question and if they do good, they can continue, if not they would need to go back to "ISO and Aperture" again.
Is this what you are after?
Sorry if am not making myself clear (my first language isn't English)
No worries, neither is mine! 
Posted by Ernie Ghiglione
