re: Time to spray top shot?

Bootlegger, I’m a little confused on what is actually a pre/post emergent. I have centipede and sprayed some weed free zone down last week. I also got some Atrizine and wanted to spray that down tomorrow. Is weed free zone a post emergent and Atrizine a pre emergent?

I also want to level the lawn with some sand/top soil mix. Should I wait until the centipede starts to green up? Also I have some spots that look like there is no grass left. Should I seed this area or just get some sod? I haven’t had much luck trying to seed.