How do these work?

ill get a site from clicking SR, fill out a few things, which then wants me to do something in a 3rd site.

How would all of these separate sites possibly get back to SR for credit?

Ive never understood ones like that.

I call them offers within offers. you never know when your done signing up for the initial offer because it asks you a hundred more things and to view a hundred more offers. (i remember a coke vs pepsi one like that).

With things like this how do you know the initial request is done?