Why do some of the floors have Stars

The floors are completely random. There is no way to make sure you get a certain floor in a particular category. You just have to wait and hope it shows up when you build.

It still means the number of floors you each have. It doesn't automatically sync every time you look at that page - I have had it be behind as much as 5 floors early on when I was building a lot. I suspect it only syncs a certain number of times per day.

As for your friend - there may be a problem with him syncing - perhaps he isn't connecting to Game Center, or has been offline when it is syncing, so you wouldn't see his floors. I know that sometimes it takes a couple of days for that screen to match what I see when I view my friend's towers, or for it to match how many floors their game says they have.