I've had the HR20 for over a year, and have been field testing the HR21 for a while now. I know things about the HR21 that I can't even talk about.
My HR21 displays 242 USAHD, 244 SCFIHD, 245 TNTHD, 247 TBSHD. I could go on, but you get the picture. No clue why your HR21 is different than mine.
Not quite sure what you're talking about here.
They are different units. The HR20 software does not drop directly onto the HR21. Each one is independent, but the goal is to make them the same as far as features go.