Marketo itself doesn't have a survey/polling feature that I'm aware of. You're going to need to find a survey/polling feature that will produce surveys and results off of Marketo data. The follow-up step in Flow 4 will basically just redirect customers to those results whether it's an entirely different page, iframed into your page, or pulled from an embed code or whatever the case may be.
If this is the case, what is the function of Marketo's poll class mktoPoll?
We do have built-in polling functionality and you have a couple options for implementing this. The way most customers would do it is something like you see here: http://go.kokopop.com/Test-Polls_test-poll-page.html
This is executed through social profile, which will actually automatically give you information about who took this action (including email address if the person shares it on their social profile). You can also optionally ask them to verify their email and opt-out/in for future communications.
Our documentation is here: http://docs.marketo.com/display/DOCS/Create+a+Poll