"Tocar" in Portuguese can mean to touch with your hand and to play an instrument.
There was a similar sentence in the English from Portuguese course. "He touched the plate." - translate to Portuguese. The official answer was "Ele tocou o prato." The native speakers had lots of fun with this one saying things like "He played it as if it were a musical instrument."
What I got out of that discussion was if you touch something with your hand, it's "tocar em." If you play a musical instrument it's "tocar" by itself.
1) So if "tocar" is followed by em, why is it not "eu toquei em gato"? 2) The correct solution that Duo gave me was: I had touched the cat. Does that mean that there is no differentiation between the perfect and the pluperfect tense? This being the first lesson on past tense, I was surprised to encounter a pluperfect at this early stage.
Toquei would usually be I touched, I had touched would be eu terei tocado, but there is some overlap between the tenses from Portuguese, tenses do not always map directly from one language to the other.