How can I ensure my respondants aren´t sending duplicates?

I run a pick´em group with my 16 friends and the only way I currently check their entries is with a simple name and last name box. I would like to limit their responses to 1 per week (or manually reset).

I encountered a problem where someone in this group is posting entries with someone else´s name.

I was thinking maybe with some kind of user and password verification.

Note that I use the same FORM for each week, I just edit the questions, so blocking the form with IP, would just block them out for the next week and I don´t want that.

Hi,

You can use the Unique Question Limit to avoid duplicate submission using the same name or same question you preferred. Here's a guide: https://www.jotform.com/help/223-how-to-set-form-limits-based-on-a-unique-question

You can also use the Unique Submission to avoid duplicate submission. The form will only accept one IP address. Here's a guide: https://www.jotform.com/help/64-how-to-set-unique-submissions-on-a-form