Difficult for me to find the answer. I've done what i needed basically using javascript but wan't to force things to be validated in PHP/seblod way independently also.

Things need to be done during the user registration process using a custom user form.

There is as anybody know a number of User Groups, I want a user to do a combination of things or one of them of my choice:

1. Backend: To allow an internet user to check only chosen three groups (one or more of them) f.e. Seblod group, Octopoos group, not f.e. standard Registered, Editor, etc. - all of them are visible during registration as a new user in a custom Seblod registration form. If this condition is not met, system will display default or custom message.

2. Displaying (still in backend): I would like to use no javascript/css method to display only 3 User Groups of my choice.

Additional information: What i've done so far: I have created a custom User form based on Seblod and added a User Group field displaying all available groups. And this point it actually works as it was originally designed.