you can’t create new FB chats. To message someone, you must have already messaged them in the past. You can’t make group chats, but can reply to existing ones.
There isn’t a thumbs up button like on facebook. I just add a thumbs up emoji reaction to the comment as a replacement. If the other person thumbs up’s, it comes through as an image.
the above linked table mentions no support for “captioned media messages”. I’m not sure what that means (is it snapchat style image with text over it?) or how to do it but maybe this matters for you
Otherwise FB messenger is one of the better supported platforms on beeper in terms of feature support.