if all of the shapes being bridged are not closed then results are unpredictable - what happens depends on your software
if any duplicate shapes are joined or bridged then all sorts of weird things may happen - it won't work right
a lot depends on the software being used as to how boolean operations work - you may have to select objects in a certain order or it may be a multi-step process
you really need to know and understand exactly how your software defines and handles nested and joined shapes, and boolean operations
or else boolean operations can be very confusing and frustrating
and if you don't know and understand how your software defines and handles nested and joined shapes then everything will be confusing and frustrating because there is only one way to do it right and a million ways to do it all wrong