DD As you intimate from your second question you already know the answer to question 1.
If you have a model or draw a diagram of a plane looking from above, and look at the where the airflow travels in a sideslip you can see that the airflow over the rudder comes from the inboard section of the wing - the flap area.
Now what happens when the disturbed airflow hits the rudder/ tailplane section depends on too many factors for there to be a straight forward answer.
I have sideslipped a number of singles and light twins without problems and I can honestly say that I have never heard of an accident due to sideslipping other than the "phantom diver" Meteor problems.
When teaching sideslipping however I do always mention that sideslipping with flap can cause problems. (Bit like on a cigarette pack and for the same reasons)