The worst part is that the 4.2% number is a floor on the actual inflation numbers. The US CPI has been lagging retail inflation for quite some time now (see 'hedonic regressions' by the BLS).
Yup.
If steak is tracked and it doubles in price, they can adjust the basket weights to reflect what they assume consumers will do: buy less beef and more chicken instead. So if Q1 steak=10 and Q2 steak=20 they might change the weights so that it's essential comparing Q1 steak to Q2 chicken. Which may be cheaper than Q1 steak, thus reducing inflation despite steak doubling in price.