Noting for future reference that despite the fact that he is 19 years old, Power will not be eligible to have his ELC slide. Assuming that he signs to finish out the season, he'll burn the first year of his three year ELC, regardless of how many games he plays.
Yep, he counts as being 20 per the CBA, even though he will not turn 20 until later in the year. IIRC, I posted the why a few pages back.