When Unique question limit is created, can someone with a different IP submit the form if they use the same value in that field?

If we use the unique code or question feild is the code set by ip address? Meaning if we use where the customer enters a code to submit the form, can onther customer from a different IP enter the same code

I think that you are mixing the strict check (which checks the IP) and the unique field value limitation.

The difference between the two is that the strict works like the Loose check I described on the previous thread: How does Loose Check on Form Submissions work?, with the difference of it also checking if the same IP was used on the server side - so if they switch browsers or clear their cookies, they would still not be able to submit the form - as long as the IP is the same.

Now the Unique Field limitation is a bit different. It is not important what is the cookie nor what is the IP, as long as that unique field is the same as some previous value, the submission will not be accepted.

You can see more about the same here: How to set Form Limits Based on a Unique Question

Now, the best unique field is email or a phone number - depending on your users.

You can however combine both Unique value and Unique Submission options to make sure that the same people can not submit the form.