I downloaded a game file size around 400MB
I read someone said, if ext is .iso it's dvd and if .bin or .cue
it's CD
is that always true?
Some files are named as DVD rip, and file type is .iso, but size is
only under 600MB
in this case do i have to burn on DVD or CD?
also burning on DVD- or DVD+ would matter?
thanks!

In general, a file thats over 700mb and has only 1 file i.e. an iso, would be a cdr, bigger than that usually means dvd, up to 4.7GB single layer, or 9.4GB dual layer.

Are there any games that use dual layer DVDs? ie any game bigger then 4.7GB

There sure are.....

You can have an 800 meg ISO file & it fits on a cd.