I have a single survey with two variations: basic and full. By default it's basic, but full questions are enabled by prefilling a hidden yes/no via an URL field.
Now, it's an open-access survey and people can fill out either basic or full, however it is implied that after filling out the basic one, they would fill out the full one too, but not all people are going to do that.
So, I'd like to let those that have filled out basic questions to fill out full questions afterwards too, and have them be in a single response.
My question is, is it possible to append existing responses like this? How?
It would also be good if it could check the uniqueness of a submitted response by comparing a hash of email + name against existing responses.

About uniqueness : why you don't activate participant and allow registering ?
 

I need people to be able to fill out multiple responses on behalf of others, but name + email must not repeat. You tell me though, maybe I'm overlooking something

Test this : manual.limesurvey.org/Participant_settin..._public_registration

Only one answer by email.

Sorry if I was being unclear: the survey has questions that ask for email and preferred name. One person should be able to fill out multiple responses, but among them the email + name must not repeat. Then, existing responses of the basic questions can be appended with the full questions, which I imagine can be done via some kind of tokens, but I can't give them out since it's an open-access survey

Validation on the name question

manual.limesurvey.org/StatFunctions
I use EMAIL and NAME for the title of the questions

1. Create an equation question (EMAILNAME) with equation set to {join(EMAILNAOK,NAME.NAOK)} (same group)
2. In NAME validation : {statCountIf(EMAILNAME.sgqa, EMAILNAME.NAOK) < 1} and set tip to : This name was already used with this email

It work only for Submitted value, if you want to really avoid duplicate {statCountIf(EMAILNAME.sgqa, EMAILNAME.NAOK, 0, 0) < 1}
 

I'm running LimeSurvey Community Edition Version 6.4.8+240221 and statCountIf is undefined

  Before using these functions the plugin must be activated in Plugin Manager. Scan the files there and then install and activate the plugin.

When there are a link : please read until end