Can a range hood vent have a 90 degree bend and vent out the wall?
In general, yes an exhaust vent (or any vent) can turn corners.  But there are many other factors to consider.

Different vent materials or dimensions resist air differently.  Different ways of turning corners resist air differently.  The best place to start looking for info on this is the vent installation manual.  It will talk about different ways to construct vents, what types of ducting corners can be used, and what size of ducting you need.  It will talk about how many feet of vent the blower can push through, and how many feet to count a corner as (typically 5').

So you know, the shallow box vents have poor airflow.  And you have to consider getting through the top-plate of the wall, which would create a huge weak point.  When we built our kitchen I was hoping for in-wall ducting.  Instead, the installers had to put a 10" circular duct up through the middle of the cabinet above the stove.