Can you apply for payperpost.com, smorty.com and other pay per post blog if you're blog is powered by Blogspot?
Yes, you can. It's not a problem as long as your blog has some original content and has been around for a while.
Yes, you can, but with your own root domain, .com, .net, etc, you will be able to earn more as advertisers prefer such blogs compared to those with a generic domain.
I think you can but from what I've seen,most advertisers won't accept those free blogs,especially bloggspot blogs.
on the other hand your blog should have some posts and regular posts to get accepted to this blog and they should rank well in terms of traffic
That's true Richie - particularly with PPP. There are others, like Blogsvertise, that make no distinction at all.