Advice on personalized links for participants

Hello PsychoPy forum,

I am running an online experiment in which participants need to train on different tasks (1 day = 1 task, total = 6 tasks on 6 consecutive days).
I want to use planned emails for participants so each participant receive 1 personalized link that invites them to perform 1 task and that is only available once. I plan to do this 6 times per person.
Each participant has a personal identifier.

Do you think that it is feasible ? Any potential issue I’m overlooking ?
I anticipate that some participants may take more than one credit by running the experiment multiple times. Any ways to prevent that ?

Thanks in advance for your recommendations.
Best,
MM