Translation:Big dog, big cat. Big mice, big cows.
Hindi doesn't have the concept of neutral. The gender (or लिंग) of an object is pretty hard to remember. German also has a sort of similar system, only they have 3 genders. However, Hindi has only male and female. In a lot of cases, the male objects end with an (aa) sound and the female with an (ii) sound. But that's not a hard and fast rule. One example is pakshi, which is male. So a dog is always male, unless you're talking about a specific dog. And a cat is always female, unless you have a special one in mind.
I doubt that. My son uses Duolingo too and loves to show me how he cansquishallthewordstogetherandstillgetit'right'.
I can't tell you how many times in the past I thought "HEY I got that RIGHT!" - but then found out I misspelled something/etc. That said, maybe you're right and I'm wrong. Although I doubt it - this time ;)
Sanskrit doesn't really have that many ones of its own, as far as I can make out it's just '|' and '||'. It seems like all old texts were in poetic forms. '|' marked the end of a line and '||' marked the end of a couplet/stanza. (I never studied Sanskrit with the attention it deserves, but I remember this much.)