Army does not do below the zone considerations until you are going for your O-5 or O-6 boards. At that time you can get looked at after 4 yrs time in grade. O-4 is a fully qualified board - not competitive so nobody gets looked at BZ.
Constructive credit for officers is usually 1:2. For every 2 yrs in a differenent AOC they will give you 1 yr towards rank. I am not sure if this works the same for reserve/guard - but that is how it is for Active. So as an example: I had a friend that graduated the same time I did from a different dental school. She had been an MSC Officer for 6 yrs. She kept all her time in service towards pay (6 yrs), and her 6 yrs as an officer was converted to a dental CPT w/ 3 yrs towards rank. She was promoted a couple of years before I was even though we entered the same time.