You have 7 in-real life days to complete the game, for more of a challenge, 5 or 3 days shall suffice.
The rules are, you cannot mine any ore, no exceptions! Stone and dirt and other variants can still be mined. Oh, and don't run your hands all over that Desert Fossils, you PC players have, because that still counts as a type of ore in my dictionary.
So, how do you get items? Just go running around like a crazy person looting chests, sometimes there are ores there. And you can get materials from enemies too.
So, yeah, not that much of a challenge until near end-game where you basically have hallowed armor as your strongest arsenal.
Good luck (especially for PC players who have to beat Moon Lord with Hallowed Armor if they join this challenge).