Cats can definitely tell if a human is a child-adult or elder. Some may not care or show that they know. But they do know.

Trust me i've done studies with my heart and feelings. Pinky swear.

Kittens meow because babies make sounds/cry

Cats meow because they realized long long ago that humans don't communicate the same way with blinks and stares (while we can and do its different than how animals do) They got tired of staring and quickly learned we are a quite loud/vocal species and will definitely respond to MeOwSsSsSs :)