google-forms
Currently when I click on the "Send Form" button in Google Forms users will be able to input the form when they know the URL.
Is it possible to grant a specific user to have access to the form?
(So I can revoke some user later without changing the URL?)
Google doesn't currently support this feature - there is no way to save a form and have a user return to it later without submitting it.
That does raise an interesting point, though. You can have the user submit the survey and edit their responses later. Instead of forcing the user to page through the rest of the survey to get to the submit button, just add a multiple choice question at the bottom of each survey page (see example below):
By using question logic, we can send survey-takers to the "Submit form" page which then gives them an "Edit this form" link that they'll need to save. Of course, when they come back, they will be starting from the beginning of the survey, but their previous answers will remain filled in.
If this all seems complicated (it is), you may want to try one of the paid survey services (I found SurveyMonkey to be a good value for the money, at least a few years ago), which make implementing this much easier (see SurveyMonkey info here).
The answer validation in Google Forms could be done with Google Apps Script after the students submit their responses, i.e. by using onFormSubmit event.
Once the answer was submitted, you could use the Class File to get properties like:
It's worth to say that in the 2014 summer Google launched Google Classroom to help teachers to manage the assignments of their classes among other tasks.
Best Answer
At this time, there is no way to limit a user to send a response, but you could allow only one response per user. See View and manage users responses