Why one person cannot submit the multiple forms by one ip/system?

when my friend tried to submit the form from the same machine the message promted that only one entry allowed , although all the details were different

I cloned your form and I found out that the Unique Submission is set to "Check cookies only". This means that the user cannot submit multiple times using the same browser.

I suggest you turn disable this if you don't want to set a limit on the submissions. You just need to go to the Form Settings and change it to "No Check". Here's a guide: https://www.jotform.com/help/64-How-to-Set-Unique-Submissions-on-a-Form

You might want to check this guide as well: https://www.jotform.com/help/223-How-to-set-Form-Limits-Based-on-a-Unique-Question

Hope that helps. Thank you.