Chop is purely a colloquial term, as you mentioned, it is based on a Hindi word.
You're not going to convince me that "Lift" is the "formal" word for Elevator, it being an American invention (well the Brits had a predecessor, called an "ascending room"
"apartment"'s etymology goes back to the 1600's, while use of the word "flat" goes to the 1800's (a Scottish word). Although 'apartment' doesn't seem to have been used as the American equivalent to "flat" until the 1800's. So we'll call that one a tie
So yeah, nice try though