the AHR can recline slightly.
My Dd has been in it for over 12 months she is a small child build wise, she has had no issues with it she sleeps in the car whenever we drive longer than 20 min. no worries.

the height of the AHR is greater than any booster seat when you have the AHR at full height.
we looked into this as DD1 is 95%tile in height she is as tall as the 4yos now and no where near going over it..