If you’re afraid that somebody’s going to copypasta wins, then why not have a flag array that says which parts of the game they completed and only handing out the reward to people who have completed all sections?

Or using the account/alt ID to hash the base address to get player/alt-specific URLs that are worthless for copypasta?

This is hardly an unsolvable problem, the only question is how abuse-proof a solution do you want (The Trapped in a Cupboard guide on the wiki?) and how much time do you want to spend on it.