Translation:The cat cleaned the kitchen this morning.
I agree that they could use some real farm terms instead of this, but it isn't totally nonsense. This is called personification, and it's quite common in literature. I think that's what they were going for, the whole "Old Macdonald had a farm" thing. I wouldn't have called that section "farm", and I wouldn't have made a farm section all about personification and nursery rhyme, but that seems to be what they did.
If sentence has ayer I can place it at the begin. And Duolingo approve it. So, I cannot do this with "Esta mañana"?
If you replace the subject of this sentence (the cat) with something more mundane (my wife), you get a normal sentence. Duo is teaching us preterite (past simple). It is the tense we use when we tell stories and what happened earlier today/yesterday/a few years ago. Very useful stuff.