1) Last I heard the iphone8's battery life is 24 hours with average use; my motoX play (a mid range phone from 2015) has the same battery life, and I use my phone all day, even to listen music with its speaker for hours (no extra recharging), and a 1080p screen, sometimes I even forget to charge it.
2) Dalvik was used by default until android 5, now the jit-compiler is called ART (we are in android 8). It's obvious that a scripting language like java will have a poorer average performance compared to a compiled language like Swift (or Objective-C previously), even in ideal conditions, however iphones are not even 2x faster than android counterparts... so kudos android developers.
3) iOS is based in BSD... so your expectations are accomplished.
I dislike android, especially for what has become, but i dislike more the apple walled garden. This is my personal opinion.