Here's my situation. I have a long list of students (each student with an ID); and each student have their own preferences on food, and games, ... (all of these data are stored on a Google Spreadsheet). I'd like to confirm all the students that the info are all correct.

I can do this by sending each student with a prefilled-link a Google Form, then after they edit, and hit submit, I'll scan and update the spreadsheet, and resend them the new link with pre-filled information that they've just editted.

However, I find it to be a little bit 'messy' (? I'm not exactly sure if this is the right word, as they have to check their emails, click on the link, and when they need to modify their data yet again, they have to find the newest email sent by me, and click on the new link).

I wonder if this can be solved just by using only Google Form (or maybe by embedding a Google Form inside another page?)? I'm thinking off creating 2 Google Forms:

1. One form for the students to enter their ID, and when they hit submit they'll be taken to the second Google Form with their newest info (fetched from the spreadsheet) pre-filled for them.
2. The second form is the form filled with their previously-entered information.

Since Google App Script will not allowed me to redirect the users to some other website (including, other Google Forms?) upon form submission, so I'm thinking of embedding the ID Google Form into my site on Google Site.

Here's my pretty bad embedding:

<!-- Normal form embed code, add an ID -->
<iframe id="gform" src="https://docs.google.com/forms/d/e/MyFirstFormURL/viewform?embedded=true" width="640" height="700" frameborder="0" marginheight="0" marginwidth="0" style="margin:0 auto; max-width:100%;">Loading…</iframe>

<script type="text/javascript">
var load = 0;

document.getElementById('gform').onload = function(){
    /*Execute on every reload on iFrame*/
    load++;
    if(load == 2){
        /*Second reload is a submit*/
        document.location = "https://docs.google.com/forms/d/e/MySecondFormURL/viewform?embedded=true";
    }
}
</script>

But I run into 2 problems (or maybe 3 problems):

1. I use onload event for the iframe to check whether the form has already been submitted; which is bad, since it will still direct me to the second page even when I hit "Clear Form".
2. I cannot read the ID the student provided inside the Google Form embedded in iframe. :(
3. Even if I can somehow read the ID in my Google Form, I have no way to externally perform a search on my spreadsheet to get the desired pre-filled link (it must be done by GAS back-end, right?)

I have some basic knowledge in programming (like a tad C, and C++; but I have very little (next to nothing) experience when it comes to web-development), I just list out everything that I have thought about, and worked on in this post. :(

Can someone give me a push? :(

Thank you so much in advance, :*