Since no one has replied you and as this comment was made five days ago. So I'll answer. Although I'm not a native Hindi speaker but atleast I know the difference between उस & वह . So, native Hindi speakers correct it if it turns out to be wrong.
Now coming straightly, वह is in subjective case like वह बिल्ली अच्छी है । That cat is nice. उस is objective case like मुझे उस बिल्ली पसन्द है । I like that cat. Hope mine clarifies your doubt.
Yes इस is the objective case of यह. उस is the objective case of वह For eg : इसका दाम क्या है ? (Literal translation is What's the cost of this (thing)? ) Vs यह कितना है ? (Literal translation is This (thing) how much is ? ) Similarly you will understand उस vs वह. Hope mine clarifies yours. Thanks. Still I'm a learner, so forgive me if there are mistakes.
James Twils, also let me remind when there's postposition like se, par, etc. I feel that the voh as well as yeh become objective us and is respectively. This observance when I come most of the Hindi sentences.
I too have not mastered it but atleast I can observe such a trend. Also see in the above sentence, If there's no postposition after kursi then definitely it's vah but there was a postposition par so it becomes us kursi. Please ignore us billi pasand hai which I said previously, I think it's wrong.
But I kept one example iska daam kya hai see there's a postposition ka so yah became is. And it is right, you can verify.
Again i hope mine clarifies your doubt.
That's wonderfully clear, Aakhil. Since it looks to me as if you may have a bit more exposure than I to Hindi, I will ask one interesting point that comes up in your writing. You seem to write the postpositions as one word with the pronoun, e.g. इसका, whereas the Duolingo program seems to write two words, इस का. Do you see it written as one word in the wild, as it were?
Thank you and btw yes it is इस का not इसका. Sorry for that, I forgot it because in colloquial level, the speakers mix these two and it sounds as a single word.
Also I feel (think) a word can't contain postposition squeezed together as a single word.
FYI, i am not able to reply at your comment below there as there was no reply option. Thus I replied at the top of your comment.