I don't think they're synonymous. "That chicken is alive", but "That is a live chicken". You certainly wouldn't say "That chicken is live" (you can say "that wire is live", but that's a different meaning). I'm not sure I can quite explain how they're different figures of speech, somebody else will be able to.
I'm sure a few lessons back I got marked wrong for writing 'it' for 'αυτό and the reason was in the comments as being 'αυτό' means 'this' and not 'it'.
"Αυτό" can mean "it, this, that".
"a few lessons back"
How are we to know which lesson you are referring to and whether it actually said that?