Why not "This is beautiful"?
then it would be "tämä on kaunis"
Is it about animal? Or only unanimated things?
can be about animals, and also se can be used instead of hän so it might be about a person as well
It can be about an animal or unanimated things or a person. In puhekieli we often use se(it) istead of hän(he/she) when talking about people
Would "on kaunis" be the same?
No, 3rd person pronouns cannot be dropped.
Why doesnt it mean "This is beautiful"