Question about calling a function from a C++ script into blueprint.

I am trying to change the difficulty of the game by entering collision detection, it is a platformer that has multiple objects that will double in speed when the difficulty is raised.

I have a couple of questions.

  1. If I have Multiple Blueprints objects that are derived from the same C++ script, will changing the originals scripts variables change them all, or would i have to write something to change each individual objects speed and velocity?

  2. How Can I access a function that is in a c++ script, into blueprint? I have been trying to enter the function via the UFUNCTION(BlueprintCallable) declaration, but in blueprint it asks for a target, and that SELF is not a valid target.