What is an Initial Preventative Physical Exam?

What is an IPPE (Initial Preventative Physical Exam) or AWV

(Annual Wellness Visit)? How often can a patient have these services, and how do they differ from a CPT Preventative Physical Exam?
-What screening code is used for a PSA? Would this be the same code used for a patient who already has BPH? Why not?
-What code or codes would you use for a Medicare patient receiving a flu shot? Does this cover the admin? Which code would you also report for administration of the vaccine?
-Is there a separate Medicare G-Code for Smoking Cessations?
-Which Colorectal Cancer Screening code should be used for a patient who has a sigmoidoscopy screening with barium enema as an alternative to a sigmoidoscopy screening without a barium enema
-List one or more things you found interesting about the Medicare Preventive Services Tool for this field trip.