Honestly, most people fail to realize an AKM is not an AK47. They're two different models and what most people would call an AK47 is in reality an AKM, AK-"Modernized", not an "old school 47".
Heck I don't think I've seen a correct AK47 in any movie, tv show, or video game as of yet; they've all been AKM's.
Minor rant but if you're into AK's then it's a difference you'd know lol.
Oh and just remembered, for (3), yes you can. There's a number of aftermarket steel barrels available for the 416 in 10-10.5" and an adjustable barrel length kit as well.
Just your friendly neighborhood narcissist gearwhore.