Challenge Mode Prizes

You get the prizes available at the time you unlock them. If the challenge changes in that time, the prizes update, but you cannot retroactively go back to claim previous prizes. You received the correct items as they were available at the time you reached each position. The UI will update, which can confuse some players into thinking they earned a new prize previously, but since each claim is time-specific, they have not (they already got a previous prize for that win, but the UI will not reflect that if the challenge changes).