Ok, maybe this is a question with an obvious answer but I am confused... up to this point I have been taught by Duo that "that/he" is expressed with वह but now I am shown उस... what is the difference?
उस is the oblique form of वह. Try to see "वह घर" as one unit which as a whole is subject to case changes.
वह घर - That house.
उस घर का/में/से/तक - Of/In/From/Up to that house.
Is उस also the oblique form of यह? How about वे ये?
No, यह becomes इस in the oblique case.
वे ये -> उन इन
Duo should use a male voice for this sentence since रहता is a masculine verb.
I want to talk in English but their was no English options here.