I want to ask users of my site several questions (using Polls). This Questionnaire form (consisting of Poll's forms and two buttons like "Ok" and "Cancel"... or just "Ok" maybe...) should be at the main page of the site.

Those who already answered questions should see results instead of the form. But I hope I can do this feature myself (or will ask for help later, if you don't mind:). The main problem so far is embedding. Or whatever I should use instead of it...

It sounds like you want functionality like that of the postticker  wrt a blog.

When i wrote a PRCase subclass, I referred extensively to the PBBlog and its associated classes for direction.