Well, to get to life, we have to have chemical elements more than just the hydrogen, helium, and a little lithium that came directly from the big bang. So for carbon, oxygen, ..., iron, have to have some big stars form, burn, and explode.
So those galaxies from 12 billion years ago didn't have much time -- ballpark only 2 billion years -- to form the elements of the periodic table.
Coming at it from our end, IIRC our planet and solar system are about 5 billion years old.
Give it, after the big bang, 4 billion years to the periodic table and another 5 billion years for life. So, that's 9 billion years, 5 billion years ago.
So don't expect much in Little Green Men ET from more than 5 billion years ago.
Since we started 5 billion years ago, we are ballpark only second generation life in this universe.
Net, mostly what's in the Hubble deep field images is too old to have much in life (anything like ours). To have a shot at seeing life, don't look back more than ballpark 5 billion years.
Since stars are burning out and the universe is expanding, are we also about the last generation of life?
Yup, it's amazing to look back 12 billion years, to see galaxies already there, with quasars and, thus, likely supermassive black holes. Amazing to guess how such big black holes formed so soon. Lots more that's amazing. Still for life, only look back about 5 billion years.
Disclosure: I'm not an astronomer!