I am new to LimeSurvey.
I need my survey to be without registration (or without e-mail and last name). But when participants want to change their answers, they can click on a link or log in to do that.

There are several ways to do that:
1) The survey is completely without registration and without tokens, but each response can have its own unique link for editing, that can be sent by the admin. (doesn't seem like something LS can do)
2) The survey requires registration, but only first name field is showed. LS automatically creates a token based on the registration. If participants want to change their response, admin sends a link with their token.
3) Something like "Save and finish later", which requires registration with username and password. Except that the name/pass registration would be at the beginning and the participants could login with the same credentials anytime later even after finishing and closing the response.
4) ...

I would appreciate any solution. Only two important things are, that 1) I don't want to communicate with participants by e-mail and I don't want them to receive any links by e-mail and 2) they must be able to edit their response later after completion.

As far as I know, there is no way to achieve both of those requirements.

1) This individualized link is basically the token link. The token is nothing else than an individualized link. You can create these token links outside of LS (there is a description in the manual on how to create those token links, you can create dummy tokens for that) and they can be sent by someone outside of Limesurvey.

What I don't get is that you don't want to communicate with them via email, but in 1) you say that the links could be sent by the admin via email. Somehow you need to communicate with them to tell them that there is a survey waiting for them...

Thank you for you replies! I (kind of) figured it out. I changed the code so right after registration, the participant is redirected to the survey with a specific token. (Instead of checking e-mail and clicking the link.)
And I removed the surname and email inputs from the registration page so there's only one field for name .
Now, the registration page looks just like an ordinary page in the survey and the survey also generates tokens, which is exactly what I wanted.

Cons: I will probably never update

You might be able to develop your custom solution as a plugin, then you could still update.

Or create a pull request so it might make it into the LS core one day.