2019 Rule change is "the effect of an illegal pitch." The illegal pitch is called a ball if the ball is the 4th ball the batter is given 1st base. Base runners only advance in a force.

2019 Rule change "adjustable knob device on bats," a knob may be adjustable but must be permanently fixed while using in a game. 

USGF has approved both Blue and Gold label Ghost Bats

What age your player is on 12/31/2019 is their playing age for the 2020 season which is Aug 1, 2019-July 31, 2020.